Key facts

Vaccines to protect against some types of Ebola have been used to control the spread of Ebola in
outbreaks. Other vaccines are in development.

Early supportive care with rehydration and the treatment of symptoms improves survival.

WHO has made strong recommendations for the use of two monoclonal antibody treatments in treating
Ebola: mAb114 (Ansuvimab; Ebanga) and REGN-EB3 (Inmazeb).

The average Ebola case fatality rate is around 50%. Case fatality rates have varied from 25–90% in past
outbreaks, depending on circumstances and the response.

Good outbreak control relies on taking many types of actions: care of patients, infection prevention and
control, disease surveillance and contact tracing, good laboratory services, safe and dignified burials,
and social mobilization.

Community engagement is key to successfully controlling outbreaks.

Overview

Ebola virus disease (EVD or Ebola) is a rare but severe illness in humans. It is often fatal.

People get infected with Ebola by touching:

infected animals when preparing, cooking or eating them

body fluids of an infected person such as saliva, urine, faeces or semen

things that have the body fluids of an infected person like clothes or sheets.

Ebola enters the body through cuts in the skin or when touching one’s eyes, nose or mouth.

Early symptoms include fever, fatigue and headache.

Some types of Ebola can be prevented with vaccines and treated with medicines.
Ebola first appeared in 1976 in 2 simultaneous outbreaks, one in what is now Nzara, South Sudan, and
the other in Yambuku, Democratic Republic of the Congo. The latter occurred in a village near the Ebola
River, from which the disease takes its name.

The virus family Filoviridae includes 3 genera: Cuevavirus, Marburgvirus, and Ebolavirus. Within the
genus Ebolavirus, 6 species have been identified: Zaire, Bundibugyo, Sudan, Taï Forest, Reston and
Bombali.

Transmission

It is thought that fruit bats of the Pteropodidae family are natural Ebola virus hosts. Ebola is introduced
into the human population through close contact with the blood, secretions, organs or other bodily
fluids of infected animals such as fruit bats, chimpanzees, gorillas, monkeys, forest antelope or
porcupines found ill or dead or in the rainforest.

Ebola then spreads through human-to-human transmission via direct contact (through broken skin or
mucous membranes) with:

blood or body fluids of a person who is sick with or has died from Ebola; and

objects that have been contaminated with body fluids (like blood, feces, vomit) from a person sick with
Ebola or the body of a person who died from Ebola.

Health-care workers have frequently been infected while treating patients with suspected or confirmed
Ebola. This occurs through close contact with patients when infection control precautions are not strictly
practiced.

Burial ceremonies that involve direct contact with the body of the deceased can also contribute to the
transmission of Ebola.

People remain infectious as long as their blood contains the virus. After recovery, there is the possibility
of sexual transmission, which can be reduced with support and information for survivors.
Pregnant women who get acute Ebola and recover from the disease may still carry the virus in
breastmilk, or in pregnancy related fluids and tissues.

For more, read the guidelines on the management of pregnancy and breastfeeding in Ebola.

Symptoms

The symptoms of Ebola infection can be sudden and include fever, fatigue, muscle pain, headache and
sore throat. These are followed by vomiting, diarrhoea, rash, and internal and external bleeding.

The time from when someone gets infected to having symptoms is usually from 2 to 21 days. A person
with Ebola can only spread the disease once they have symptoms. People can spread Ebola for as long as
their body contains the virus, even after they have died.

After recovering from Ebola, some people may have symptoms for two years or longer. These symptoms
can include:

feeling tired

headache

muscle and joint pain

eye pain and vision problems

weight gain

belly pain and loss of appetite

hair loss and skin problems

trouble sleeping

memory loss

hearing loss

depression and anxiety.

People should speak to a health-care professional if they have:

symptoms and have been in an area known to have Ebola, or

been in contact with someone who may have had Ebola.

Diagnosis

It can be difficult to clinically distinguish Ebola virus disease from other infectious diseases such as
malaria, typhoid fever and meningitis. Many symptoms of pregnancy and Ebola disease are also quite
similar. Because of risks to the pregnancy and themselves, pregnant women should ideally be tested
rapidly if Ebola is suspected.

Confirmation that symptoms are caused by Ebola virus infection are made using the following diagnostic
methods:

antibody-capture enzyme-linked immunosorbent assay (ELISA)

antigen-capture detection tests

serum neutralization test

reverse transcriptase polymerase chain reaction (RT-PCR) assay

electron microscopy

virus isolation by cell culture.

Diagnostic tests evaluated through the WHO emergency use assessment and listing process can be seen
here.

Treatment

People with symptoms of Ebola should get medical care immediately. Early care improves a person's
chances of surviving Ebola.

Treatment includes oral or intravenous fluids and medicines provided in the hospital.
It is not safe to care for people with Ebola at home, because the person may make other people sick. At
home, they will not receive the same level of care they can get from professionals.

There is an effective vaccine for the Zaire type of Ebola, which is mostly found in Guinea and the
Democratic Republic of the Congo. It is treated with antibodies. These antibody medicines are given
intravenously and increase the chances of survival.

Research is ongoing to find vaccines and treatments for other types of Ebola.

For all types of Ebola, supportive treatments save lives and include the following:

oral or intravenous fluids

blood transfusions

medicines for other infections the person may have, such as malaria

medicines for pain, nausea, vomiting and diarrhoea.

WHO has guidance that outlines the optimized supportive care Ebola patients should receive, from the
relevant tests to administer, to managing pain, nutrition and co-infections (such as malaria), and other
approaches that put the patient on the best path to recovery.

In the 2018–2020 Ebola outbreak in the Democratic Republic of the Congo, the first-ever multi-drug
randomized control trial was conducted to evaluate the effectiveness and safety of drugs used in the
treatment of Ebola patients. WHO has living guidance on the recommended treatments and approaches.

More information on Ebola clinical management

Prevention and control

People can protect themselves from getting Ebola by:

washing hands

avoiding touching the body fluids of people who have, or may have, Ebola

not touching the bodies of people who have died from Ebola

getting the Ebola vaccine if they are at risk for the Zaire type of Ebola.

The Ervebo vaccine has been shown to be effective in protecting people from the species Zaire
ebolavirus and is recommended by the Strategic Advisory Group of Experts on Immunization as part of a
broader set of Ebola outbreak response tools.

WHO prequalifies Ebola vaccine, paving the way for its use in high-risk countries

Good outbreak control relies on applying a package of interventions, including case management,
surveillance and contact tracing, a good laboratory service, safe burials and social mobilisation.
Community engagement is key to successfully controlling outbreaks. Raising awareness of risk factors
for Ebola infection and protective measures (including vaccination) that individuals can take is an
effective way to reduce human transmission. Risk reduction messaging should focus on several factors:

reducing the risk of wildlife-to-human transmission

reducing the risk of human-to-human transmission

outbreak containment measures, including safe and dignified burial of the dead

reducing the risk of possible sexual transmission

reducing the risk of transmission from pregnancy related fluids and tissue.

Health-care workers should always take standard precautions when caring for patients, regardless of
their presumed diagnosis. These include basic hand hygiene, respiratory hygiene, use of personal
protective equipment (to block splashes or other contact with infected materials), safe injection
practices and safe burial practices.

Health-care workers caring for patients with suspected or confirmed Ebola virus should apply extra
infection control measures to prevent contact with the patient’s blood and body fluids and
contaminated surfaces or materials such as clothing and bedding.
Laboratory workers are also at risk. Samples taken from humans and animals for investigation of Ebola
infection should be handled by trained staff and processed in suitably equipped laboratories.

WHO has developed detailed advice on Ebola infection prevention and control:

Infection prevention and control guidance for care of patients with suspected or confirmed Filovirus
haemorrhagic fever in health-care settings, with focus on Ebola

WHO response

WHO works with countries to prevent Ebola outbreaks by maintaining surveillance for Ebola virus
disease and supporting at-risk countries to develop preparedness plans. This document provides overall
guidance for control of Ebola and Marburg virus outbreaks:

Ebola and Marburg virus disease epidemics: preparedness, alert, control, and evaluation

When an outbreak is detected, WHO responds by supporting community engagement, disease

detection, contact tracing, vaccination, case management, laboratory services, infection control,
logistics, and training and assistance with safe and dignified burial practices.

WHO has a range of advice and guidance for managing Ebola outbreaks:

Clinical management

Disease outbreaks

Health product policy and standards - vaccine standardization

Medical devices for Ebola outbreak

Sexual and Reproductive Health and Research (SRH) and Ebola

Ebola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic
fever in humans and other primates, caused by ebolaviruses.[1] Symptoms typically start anywhere
between two days and three weeks after infection.[3] The first symptoms are usually fever, sore throat,
muscle pain, and headaches.[1] These are usually followed by vomiting, diarrhoea, rash and decreased
liver and kidney function,[1] at which point some people begin to bleed both internally and externally.
[1] It kills between 25% and 90% of those infected – about 50% on average.[1] Death is often due to
shock from fluid loss, and typically occurs between six and 16 days after the first symptoms appear.[2]
Early treatment of symptoms increases the survival rate considerably compared to late start.[4] An
Ebola vaccine was approved by the US FDA in December 2019.

Ebola

Other names

Ebola haemorrhagic fever (EHF), Ebola virus disease

Two nurses standing near Mayinga N'Seka, a nurse with Ebola virus disease in the 1976 outbreak in
Zaire. N'Seka died a few days later. The nurses are not wearing proper protective equipment.

Specialty

Infectious disease

Symptoms

Fever, sore throat, muscular pain, headaches, diarrhoea, bleeding[1]

Complications

shock from fluid loss[2]

Usual onset

Two days to three weeks post exposure[1]

Causes

Ebolaviruses spread by direct contact[1]

Diagnostic method

Finding the virus, viral RNA, or antibodies in blood[1]

Differential diagnosis

Malaria, cholera, typhoid fever, meningitis, other viral haemorrhagic fevers[1]

Prevention

Coordinated medical services, careful handling of bushmeat[1]

Treatment
Supportive care[1]

Medication

Atoltivimab/maftivimab/odesivimab (Inmazeb)

Prognosis

25–90% mortality[1]

The virus spreads through direct contact with body fluids, such as blood from infected humans or other
animals,[1] or from contact with items that have recently been contaminated with infected body fluids.
[1] There have been no documented cases, either in nature or under laboratory conditions, of spread
through the air between humans or other primates.[5] After recovering from Ebola, semen or breast
milk may continue to carry the virus for anywhere between several weeks to several months.[1][6][7]
Fruit bats are believed to be the normal carrier in nature; they are able to spread the virus without being
affected by it.[1] The symptoms of Ebola may resemble those of several other diseases, including
malaria, cholera, typhoid fever, meningitis and other viral hemorrhagic fevers.[1] Diagnosis is confirmed
by testing blood samples for the presence of viral RNA, viral antibodies or the virus itself.[1][8]

Control of outbreaks requires coordinated medical services and community engagement,[1] including
rapid detection, contact tracing of those exposed, quick access to laboratory services, care for those
infected, and proper disposal of the dead through cremation or burial.[1][9] Prevention measures
involve wearing proper protective clothing and washing hands when in close proximity to patients and
while handling potentially infected bushmeat, as well as thoroughly cooking bushmeat.[1] An Ebola
vaccine was approved by the US FDA in December 2019.[10] While there is no approved treatment for
Ebola as of 2019,[11] two treatments (atoltivimab/maftivimab/odesivimab and ansuvimab) are
associated with improved outcomes.[12] Supportive efforts also improve outcomes.[1] These include
oral rehydration therapy (drinking slightly sweetened and salty water) or giving intravenous fluids, and
treating symptoms.[1] In October 2020, atoltivimab/maftivimab/odesivimab (Inmazeb) was approved
for medical use in the United States to treat the disease caused by Zaire ebolavirus.[13]

History and name

Ebola was first identified in 1976, in two simultaneous outbreaks, one in Nzara (a town in South Sudan)
and the other in Yambuku (the Democratic Republic of the Congo), a village near the Ebola River, for
which the disease was named.[1] Ebola outbreaks occur intermittently in tropical regions of sub-Saharan
Africa.[1] Between 1976 and 2012, according to the World Health Organization, there were 24 outbreaks
of Ebola resulting in a total of 2,387 cases, and 1,590 deaths.[1][14] The largest Ebola outbreak to date
was an epidemic in West Africa from December 2013 to January 2016, with 28,646 cases and 11,323
deaths.[15][16][17] On 29 March 2016, it was declared to no longer be an emergency.[18] Other
outbreaks in Africa began in the Democratic Republic of the Congo in May 2017,[19][20] and 2018.[21]
[22] In July 2019, the World Health Organization declared the Congo Ebola outbreak a world health
emergency.[23]

Signs and symptoms

Signs and symptoms of Ebola[24]

Onset

The length of time between exposure to the virus and the development of symptoms (incubation
period) is between 2 and 21 days,[1][24] and usually between 4 and 10 days.[25] However, recent
estimates based on mathematical models predict that around 5% of cases may take longer than 21 days
to develop.[26]

Symptoms usually begin with a sudden influenza-like stage characterised by fatigue, fever, weakness,
decreased appetite, muscular pain, joint pain, headache, and sore throat.[1][25][27][28] The fever is
usually higher than 38.3 °C (101 °F).[29] This is often followed by nausea, vomiting, diarrhoea,
abdominal pain, and sometimes hiccups.[28][30] The combination of severe vomiting and diarrhoea
often leads to severe dehydration.[31] Next, shortness of breath and chest pain may occur, along with
swelling, headaches, and confusion.[28] In about half of the cases, the skin may develop a
maculopapular rash, a flat red area covered with small bumps, five to seven days after symptoms begin.

Bleeding

In some cases, internal and external bleeding may occur.[1] This typically begins five to seven days after
the first symptoms.[32] All infected people show some decreased blood clotting.[29] Bleeding from
mucous membranes or from sites of needle punctures has been reported in 40–50% of cases.[33] This
may cause vomiting blood, coughing up of blood, or blood in stool.[34] Bleeding into the skin may create
petechiae, purpura, ecchymoses or haematomas (especially around needle injection sites).[35] Bleeding
into the whites of the eyes may also occur.[36] Heavy bleeding is uncommon; if it occurs, it is usually in
the gastrointestinal tract.[37] The incidence of bleeding into the gastrointestinal tract was reported to
be ~58% in the 2001 outbreak in Gabon,[38] but in the 2014–15 outbreak in the US it was ~18%,[39]
possibly due to improved prevention of disseminated intravascular coagulation.[31]

Recovery or death
Recovery may begin between seven and 14 days after first symptoms.[28] Death, if it occurs, follows
typically six to sixteen days from first symptoms and is often due to shock from fluid loss.[2] In general,
bleeding often indicates a worse outcome, and blood loss may result in death.[27] People are often in a
coma near the end of life.[28]

Those who survive often have ongoing muscular and joint pain, liver inflammation, and decreased
hearing, and may have continued tiredness, continued weakness, decreased appetite, and difficulty
returning to pre-illness weight.[28][40] Problems with vision may develop.[41] It is recommended that
survivors of EVD wear condoms for at least twelve months after initial infection or until the semen of a
male survivor tests negative for Ebola virus on two separate occasions.[42]

Survivors develop antibodies against Ebola that last at least 10 years, but it is unclear whether they are
immune to additional infections.[43]

Cause

EVD in humans is caused by four of six viruses of the genus Ebolavirus. The four are Bundibugyo virus
(BDBV), Sudan virus (SUDV), Taï Forest virus (TAFV) and one simply called Ebola virus (EBOV, formerly
Zaire Ebola virus).[44] EBOV, species Zaire ebolavirus, is the most dangerous of the known EVD-causing
viruses, and is responsible for the largest number of outbreaks.[45] The fifth and sixth viruses, Reston
virus (RESTV) and Bombali virus (BOMV),[46] are not thought to cause disease in humans, but have
caused disease in other primates.[47][48] All six viruses are closely related to marburgviruses.[44]

Virology

Main articles: Ebolavirus (taxonomic group) and Ebola virus (specific virus)

Electron micrograph of an Ebola virus virion

Ebolaviruses contain single-stranded, non-infectious RNA genomes.[49] Ebolavirus genomes contain

seven genes including 3'-UTR-NP-VP35-VP40-GP-VP30-VP24-L-5'-UTR.[35][50] The genomes of the five
different ebolaviruses (BDBV, EBOV, RESTV, SUDV and TAFV) differ in sequence and the number and
location of gene overlaps. As with all filoviruses, ebolavirus virions are filamentous particles that may
appear in the shape of a shepherd's crook, of a "U" or of a "6," and they may be coiled, toroid or
branched.[50][51] In general, ebolavirions are 80 nanometers (nm) in width and may be as long as
14,000 nm.[52]
Their life cycle is thought to begin with a virion attaching to specific cell-surface receptors such as C-type
lectins, DC-SIGN, or integrins, which is followed by fusion of the viral envelope with cellular membranes.
[53] The virions taken up by the cell then travel to acidic endosomes and lysosomes where the viral
envelope glycoprotein GP is cleaved.[53] This processing appears to allow the virus to bind to cellular
proteins enabling it to fuse with internal cellular membranes and release the viral nucleocapsid.[53] The
Ebolavirus structural glycoprotein (known as GP1,2) is responsible for the virus' ability to bind to and
infect targeted cells.[54] The viral RNA polymerase, encoded by the L gene, partially uncoats the
nucleocapsid and transcribes the genes into positive-strand mRNAs, which are then translated into
structural and nonstructural proteins

The most abundant protein produced is the nucleoprotein, whose concentration in the host cell
determines when L switches from gene transcription to genome replication. Replication of the viral
genome results in full-length, positive-strand antigenomes that are, in turn, transcribed into genome
copies of negative-strand virus progeny.[55] Newly synthesised structural proteins and genomes self-
assemble and accumulate near the inside of the cell membrane. Virions bud off from the cell, gaining
their envelopes from the cellular membrane from which they bud. The mature progeny particles then
infect other cells to repeat the cycle. The genetics of the Ebola virus are difficult to study because of
EBOV's virulent characteristics.[56]

Transmission

Life cycles of the Ebolavirus

An illustration of safe burial practices

It is believed that between people, Ebola disease spreads only by direct contact with the blood or other
body fluids of a person who has developed symptoms of the disease.[57][58][59] Body fluids that may
contain Ebola viruses include saliva, mucus, vomit, feces, sweat, tears, breast milk, urine and semen.[6]
[43] The WHO states that only people who are very sick are able to spread Ebola disease in saliva, and
the virus has not been reported to be transmitted through sweat. Most people spread the virus through
blood, feces and vomit.[60] Entry points for the virus include the nose, mouth, eyes, open wounds, cuts
and abrasions.[43] Ebola may be spread through large droplets; however, this is believed to occur only
when a person is very sick.[61] This contamination can happen if a person is splashed with droplets.[61]
Contact with surfaces or objects contaminated by the virus, particularly needles and syringes, may also
transmit the infection.[62][63] The virus is able to survive on objects for a few hours in a dried state, and
can survive for a few days within body fluids outside of a person.[43][64]
The Ebola virus may be able to persist for more than three months in the semen after recovery, which
could lead to infections via sexual intercourse.[6][65][66] Virus persistence in semen for over a year has
been recorded in a national screening programme.[67] Ebola may also occur in the breast milk of
women after recovery, and it is not known when it is safe to breastfeed again.[7] The virus was also
found in the eye of one patient, in 2014, two months after it was cleared from his blood.[68] Otherwise,
people who have recovered are not infectious.[62]

The potential for widespread infections in countries with medical systems capable of observing correct
medical isolation procedures is considered low.[69] Usually when someone has symptoms of the
disease, they are unable to travel without assistance.[70]

Dead bodies remain infectious; thus, people handling human remains in practices such as traditional
burial rituals or more modern processes such as embalming are at risk.[69] Of the cases of Ebola
infections in Guinea during the 2014 outbreak, 69% are believed to have been contracted via
unprotected (or unsuitably protected) contact with infected corpses during certain Guinean burial
rituals.[71][72]

Health-care workers treating people with Ebola are at greatest risk of infection.[62] The risk increases
when they do not have appropriate protective clothing such as masks, gowns, gloves and eye
protection; do not wear it properly; or handle contaminated clothing incorrectly.[62] This risk is
particularly common in parts of Africa where the disease mostly occurs and health systems function
poorly.[73] There has been transmission in hospitals in some African countries that reuse hypodermic
needles.[74][75] Some health-care centres caring for people with the disease do not have running
water.[76] In the United States the spread to two medical workers treating infected patients prompted
criticism of inadequate training and procedures.[77]

Human-to-human transmission of EBOV through the air has not been reported to occur during EVD
outbreaks,[5] and airborne transmission has only been demonstrated in very strict laboratory
conditions, and then only from pigs to primates, but not from primates to primates.[57][63] Spread of
EBOV by water, or food other than bushmeat, has not been observed.[62][63] No spread by mosquitos
or other insects has been reported.[62] Other possible methods of transmission are being studied.[64]
Airborne transmission among humans is theoretically possible due to the presence of Ebola virus
particles in saliva, which can be discharged into the air with a cough or sneeze, but observational data
from previous epidemics suggests the actual risk of airborne transmission is low.[78] A number of
studies examining airborne transmission broadly concluded that transmission from pigs to primates
could happen without direct contact because, unlike humans and primates, pigs with EVD get very high
ebolavirus concentrations in their lungs, and not their bloodstream.[79] Therefore, pigs with EVD can
spread the disease through droplets in the air or on the ground when they sneeze or cough.[80] By
contrast, humans and other primates accumulate the virus throughout their body and specifically in
their blood, but not very much in their lungs.[80] It is believed that this is the reason researchers have
observed pig to primate transmission without physical contact, but no evidence has been found of
primates being infected without actual contact, even in experiments where infected and uninfected
primates shared the same air.[79][80]

Initial case

Bushmeat having been smoked in Ghana. In Africa, wild animals including fruit bats are hunted for food
and are referred to as bushmeat.[81][82] In equatorial Africa, human consumption of bushmeat has
been linked to animal-to-human transmission of diseases, including Ebola.[83]

Although it is not entirely clear how Ebola initially spreads from animals to humans, the spread is
believed to involve direct contact with an infected wild animal or fruit bat.[62] Besides bats, other wild
animals that are sometimes infected with EBOV include several species of monkeys such as baboons,
great apes (chimpanzees and gorillas), and duikers (a species of antelope).[84]

Animals may become infected when they eat fruit partially eaten by bats carrying the virus.[85] Fruit
production, animal behavior and other factors may trigger outbreaks among animal populations.[85]

Evidence indicates that both domestic dogs and pigs can also be infected with EBOV.[86] Dogs do not
appear to develop symptoms when they carry the virus, and pigs appear to be able to transmit the virus
to at least some primates.[86] Although some dogs in an area in which a human outbreak occurred had
antibodies to EBOV, it is unclear whether they played a role in spreading the disease to people.[86]

Reservoir

The natural reservoir for Ebola has yet to be confirmed; however, bats are considered to be the most
likely candidate.[63] Three types of fruit bats (Hypsignathus monstrosus, Epomops franqueti and
Myonycteris torquata) were found to possibly carry the virus without getting sick.[87] As of 2013,
whether other animals are involved in its spread is not known.[86] Plants, arthropods, rodents, and birds
have also been considered possible viral reservoirs.[1][31]

Bats were known to roost in the cotton factory in which the first cases of the 1976 and 1979 outbreaks
were observed, and they have also been implicated in Marburg virus infections in 1975 and 1980.[88] Of
24 plant and 19 vertebrate species experimentally inoculated with EBOV, only bats became infected.[89]
The bats displayed no clinical signs of disease, which is considered evidence that these bats are a
reservoir species of EBOV. In a 2002–2003 survey of 1,030 animals including 679 bats from Gabon and
the Republic of the Congo, immunoglobulin G (IgG) immune defense molecules indicative of Ebola
infection were found in three bat species; at various periods of study, between 2.2 and 22.6% of bats
were found to contain both RNA sequences and IgG molecules indicating Ebola infection.[90] Antibodies
against Zaire and Reston viruses have been found in fruit bats in Bangladesh, suggesting that these bats
are also potential hosts of the virus and that the filoviruses are present in Asia

Between 1976 and 1998, in 30,000 mammals, birds, reptiles, amphibians and arthropods sampled from
regions of EBOV outbreaks, no Ebola virus was detected apart from some genetic traces found in six
rodents (belonging to the species Mus setulosus and Praomys) and one shrew (Sylvisorex ollula)
collected from the Central African Republic.[88][92] However, further research efforts have not
confirmed rodents as a reservoir.[93] Traces of EBOV were detected in the carcasses of gorillas and
chimpanzees during outbreaks in 2001 and 2003, which later became the source of human infections.
However, the high rates of death in these species resulting from EBOV infection make it unlikely that
these species represent a natural reservoir for the virus.[88]

Deforestation has been mentioned as a possible contributor to recent outbreaks, including the West
African Ebola virus epidemic. Index cases of EVD have often been close to recently deforested lands.[94]
[95]

Pathophysiology

Pathogenesis schematic

Like other filoviruses, EBOV replicates very efficiently in many cells, producing large amounts of virus in
monocytes, macrophages, dendritic cells and other cells including liver cells, fibroblasts, and adrenal
gland cells.[96] Viral replication triggers high levels of inflammatory chemical signals and leads to a
septic state.[40]
EBOV is thought to infect humans through contact with mucous membranes or skin breaks.[57] After
infection, endothelial cells (cells lining the inside of blood vessels), liver cells, and several types of
immune cells such as macrophages, monocytes, and dendritic cells are the main targets of attack.[57]
Following infection, immune cells carry the virus to nearby lymph nodes where further reproduction of
the virus takes place.[57] From there the virus can enter the bloodstream and lymphatic system and
spread throughout the body.[57] Macrophages are the first cells infected with the virus, and this
infection results in programmed cell death.[52] Other types of white blood cells, such as lymphocytes,
also undergo programmed cell death leading to an abnormally low concentration of lymphocytes in the
blood.[57] This contributes to the weakened immune response seen in those infected with EBOV.[57]

Endothelial cells may be infected within three days after exposure to the virus.[52] The breakdown of
endothelial cells leading to blood vessel injury can be attributed to EBOV glycoproteins. This damage
occurs due to the synthesis of Ebola virus glycoprotein (GP), which reduces the availability of specific
integrins responsible for cell adhesion to the intercellular structure and causes liver damage, leading to
improper clotting. The widespread bleeding that occurs in affected people causes swelling and shock
due to loss of blood volume.[97] The dysfunctional bleeding and clotting commonly seen in EVD has
been attributed to increased activation of the extrinsic pathway of the coagulation cascade due to
excessive tissue factor production by macrophages and monocytes.[25]

After infection, a secreted glycoprotein, small soluble glycoprotein (sGP or GP) is synthesised. EBOV
replication overwhelms protein synthesis of infected cells and the host immune defences. The GP forms
a trimeric complex, which tethers the virus to the endothelial cells. The sGP forms a dimeric protein that
interferes with the signalling of neutrophils, another type of white blood cell. This enables the virus to
evade the immune system by inhibiting early steps of neutrophil activation.[medical citation needed]
Furthermore, the virus is capable of hijacking cellular metabolism. Studies have shown that Ebola virus-
like particles can reprogram metabolism in both vascular and immune cells.[98]

Immune system evasion

Filoviral infection also interferes with proper functioning of the innate immune system.[53][55] EBOV
proteins blunt the human immune system's response to viral infections by interfering with the cells'
ability to produce and respond to interferon proteins such as interferon-alpha, interferon-beta, and
interferon gamma.[54][99]
The VP24 and VP35 structural proteins of EBOV play a key role in this interference. When a cell is
infected with EBOV, receptors located in the cell's cytosol (such as RIG-I and MDA5) or outside of the
cytosol (such as Toll-like receptor 3 (TLR3), TLR7, TLR8 and TLR9) recognise infectious molecules
associated with the virus.[54] On TLR activation, proteins including interferon regulatory factor 3 and
interferon regulatory factor 7 trigger a signalling cascade that leads to the expression of type 1
interferons.[54] The type 1 interferons are then released and bind to the IFNAR1 and IFNAR2 receptors
expressed on the surface of a neighbouring cell.[54] Once interferon has bound to its receptors on the
neighbouring cell, the signalling proteins STAT1 and STAT2 are activated and move to the cell's nucleus.
[54] This triggers the expression of interferon-stimulated genes, which code for proteins with antiviral
properties.[54] EBOV's V24 protein blocks the production of these antiviral proteins by preventing the
STAT1 signalling protein in the neighbouring cell from entering the nucleus.[54] The VP35 protein
directly inhibits the production of interferon-beta.[99] By inhibiting these immune responses, EBOV may
quickly spread throughout the body.[52]

Diagnosis

When EVD is suspected, travel, work history, and exposure to wildlife are important factors with respect
to further diagnostic efforts.[100]

Laboratory testing

Possible non-specific laboratory indicators of EVD include a low platelet count; an initially decreased
white blood cell count followed by an increased white blood cell count; elevated levels of the liver
enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST); and abnormalities in
blood clotting often consistent with disseminated intravascular coagulation (DIC) such as a prolonged
prothrombin time, partial thromboplastin time, and bleeding time.[101] Filovirions such as EBOV may be
identified by their unique filamentous shapes in cell cultures examined with electron microscopy.[102]

The specific diagnosis of EVD is confirmed by isolating the virus, detecting its RNA or proteins, or
detecting antibodies against the virus in a person's blood.[103] Isolating the virus by cell culture,
detecting the viral RNA by polymerase chain reaction (PCR)[8][25] and detecting proteins by enzyme-
linked immunosorbent assay (ELISA) are methods best used in the early stages of the disease and also
for detecting the virus in human remains.[8][103] Detecting antibodies against the virus is most reliable
in the later stages of the disease and in those who recover.[103] IgM antibodies are detectable two days
after symptom onset and IgG antibodies can be detected six to 18 days after symptom onset.[25] During
an outbreak, isolation of the virus with cell culture methods is often not feasible. In field or mobile
hospitals, the most common and sensitive diagnostic methods are real-time PCR and ELISA.[104] In
2014, with new mobile testing facilities deployed in parts of Liberia, test results were obtained 3–5
hours after sample submission.[105] In 2015, a rapid antigen test which gives results in 15 minutes was
approved for use by WHO.[106] It is able to confirm Ebola in 92% of those affected and rule it out in 85%
of those not affected.

Differential diagnosis

Early symptoms of EVD may be similar to those of other diseases common in Africa, including malaria
and dengue fever.[27] The symptoms are also similar to those of other viral haemorrhagic fevers such as
Marburg virus disease, Crimean–Congo haemorrhagic fever, and Lassa fever.[107][108]

The complete differential diagnosis is extensive and requires consideration of many other infectious
diseases such as typhoid fever, shigellosis, rickettsial diseases, cholera, sepsis, borreliosis, EHEC enteritis,
leptospirosis, scrub typhus, plague, Q fever, candidiasis, histoplasmosis, trypanosomiasis, visceral
leishmaniasis, measles, and viral hepatitis among others.[109]

Non-infectious diseases that may result in symptoms similar to those of EVD include acute
promyelocytic leukaemia, haemolytic uraemic syndrome, snake envenomation, clotting factor
deficiencies/platelet disorders, thrombotic thrombocytopenic purpura, hereditary haemorrhagic
telangiectasia, Kawasaki disease, and warfarin poisoning.[104][110][111][112]

Prevention

Main article: Prevention of viral hemorrhagic fever

Vaccines

Main article: Ebola vaccine

An Ebola vaccine, rVSV-ZEBOV, was approved in the United States in December 2019.[10] It appears to
be fully effective ten days after being given.[10] It was studied in Guinea between 2014 and 2016.[10]
More than 100,000 people have been vaccinated against Ebola as of 2019.[113] The WHO reported that
approximately 345,000 people were given the vaccine during the Kivu Ebola epidemic from 2018 to
2020.[114]

Infection control

VHF isolation precautions poster

Community awareness of the benefits on survival chances of admitting cases early is important for the
infected and infection control [4]

Caregivers

British woman wearing protective gear

People who care for those infected with Ebola should wear protective clothing including masks, gloves,
gowns and goggles.[115] The U.S. Centers for Disease Control (CDC) recommend that the protective gear
leaves no skin exposed.[116] These measures are also recommended for those who may handle objects
contaminated by an infected person's body fluids.[117] In 2014, the CDC began recommending that
medical personnel receive training on the proper suit-up and removal of personal protective equipment
(PPE); in addition, a designated person, appropriately trained in biosafety, should be watching each step
of these procedures to ensure they are done correctly.[116] In Sierra Leone, the typical training period
for the use of such safety equipment lasts approximately 12 days.[118] In 2022 in Uganda, lighter
personal protection equipment has become available as well as possibilities to monitor and
communicate with patients from windows in the treatment tents until it is necessary to enter if e.g. a
patient's oxygen levels drop. [4]

Patients and household members

The infected person should be in barrier-isolation from other people.[115] All equipment, medical
waste, patient waste and surfaces that may have come into contact with body fluids need to be
disinfected.[117] During the 2014 outbreak, kits were put together to help families treat Ebola disease in
their homes, which included protective clothing as well as chlorine powder and other cleaning supplies.
[119] Education of caregivers in these techniques, and providing such barrier-separation supplies has
been a priority of Doctors Without Borders.[120]

Disinfection

Ebolaviruses can be eliminated with heat (heating for 30 to 60 minutes at 60 °C or boiling for five
minutes). To disinfect surfaces, some lipid solvents such as some alcohol-based products, detergents,
sodium hypochlorite (bleach) or calcium hypochlorite (bleaching powder), and other suitable
disinfectants may be used at appropriate concentrations.[84][121]

General population
Education of the general public about the risk factors for Ebola infection and of the protective measures
individuals may take to prevent infection is recommended by the World Health Organization.[1] These
measures include avoiding direct contact with infected people and regular hand washing using soap and
water.[122]

Bushmeat

Bushmeat, an important source of protein in the diet of some Africans, should be handled and prepared
with appropriate protective clothing and thoroughly cooked before consumption.[1] Some research
suggests that an outbreak of Ebola disease in the wild animals used for consumption may result in a
corresponding human outbreak. Since 2003, such animal outbreaks have been monitored to predict and
prevent Ebola outbreaks in humans.[123]

Corpses, burial

If a person with Ebola disease dies, direct contact with the body should be avoided.[115] Certain burial
rituals, which may have included making various direct contacts with a dead body, require reformulation
so that they consistently maintain a proper protective barrier between the dead body and the living.
[124][125][126] Social anthropologists may help find alternatives to traditional rules for burials.[127]

Transport, travel, contact

Transportation crews are instructed to follow a certain isolation procedure, should anyone exhibit
symptoms resembling EVD.[128] As of August 2014, the WHO does not consider travel bans to be useful
in decreasing spread of the disease.[70] In October 2014, the CDC defined four risk levels used to
determine the level of 21-day monitoring for symptoms and restrictions on public activities.[129] In the
United States, the CDC recommends that restrictions on public activity, including travel restrictions, are
not required for the following defined risk levels:[129]

having been in a country with widespread Ebola disease transmission and having no known exposure
(low risk); or having been in that country more than 21 days ago (no risk)

encounter with a person showing symptoms; but not within three feet of the person with Ebola without
wearing PPE; and no direct contact with body fluids

having had brief skin contact with a person showing symptoms of Ebola disease when the person was
believed to be not very contagious (low risk)
in countries without widespread Ebola disease transmission: direct contact with a person showing
symptoms of the disease while wearing PPE (low risk)

contact with a person with Ebola disease before the person was showing symptoms (no risk).

The CDC recommends monitoring for the symptoms of Ebola disease for those both at "low risk" and at
higher risk

Laboratory

In laboratories where diagnostic testing is carried out, biosafety level 4-equivalent containment is
required.[130] Laboratory researchers must be properly trained in BSL-4 practices and wear proper PPE.
[130]

Isolation

Isolation refers to separating those who are sick from those who are not. Quarantine refers to
separating those who may have been exposed to a disease until they either show signs of the disease or
are no longer at risk.[131] Quarantine, also known as enforced isolation, is usually effective in
decreasing spread.[132][133] Governments often quarantine areas where the disease is occurring or
individuals who may transmit the disease outside of an initial area.[134] In the United States, the law
allows quarantine of those infected with ebolaviruses.[135][136]

Contact tracing

Contact tracing is considered important to contain an outbreak. It involves finding everyone who had
close contact with infected individuals and monitoring them for signs of illness for 21 days. If any of
these contacts comes down with the disease, they should be isolated, tested and treated. Then the
process is repeated, tracing the contacts' contacts.[137][138]

Management

As of 2019 two treatments (atoltivimab/maftivimab/odesivimab and ansuvimab) are associated with

improved outcomes.[11][12] The U.S. Food and Drug Administration (FDA) advises people to be careful
of advertisements making unverified or fraudulent claims of benefits supposedly gained from various
anti-Ebola products.[139][140]
In October 2020, the U.S. Food and Drug Administration (FDA) approved
atoltivimab/maftivimab/odesivimab with an indication for the treatment of infection caused by Zaire
ebolavirus.[13]

Standard support

A hospital isolation ward in Gulu, Uganda, during the October 2000 outbreak

Treatment is primarily supportive in nature.[141] Early supportive care with rehydration and
symptomatic treatment improves survival.[1] Rehydration may be via the oral or intravenous route.
[141] These measures may include pain management, and treatment for nausea, fever, and anxiety.
[141] The World Health Organization (WHO) recommends avoiding aspirin or ibuprofen for pain
management, due to the risk of bleeding associated with these medications.[142]

Blood products such as packed red blood cells, platelets, or fresh frozen plasma may also be used.[141]
Other regulators of coagulation have also been tried including heparin in an effort to prevent
disseminated intravascular coagulation and clotting factors to decrease bleeding.[141] Antimalarial
medications and antibiotics are often used before the diagnosis is confirmed,[141] though there is no
evidence to suggest such treatment helps. Several experimental treatments are being studied.[143]

Where hospital care is not possible, the WHO's guidelines for home care have been relatively successful.
Recommendations include using towels soaked in a bleach solution when moving infected people or
bodies and also applying bleach on stains. It is also recommended that the caregivers wash hands with
bleach solutions and cover their mouth and nose with a cloth.[144]

Intensive care

Intensive care is often used in the developed world.[35] This may include maintaining blood volume and
electrolytes (salts) balance as well as treating any bacterial infections that may develop.[35] Dialysis may
be needed for kidney failure, and extracorporeal membrane oxygenation may be used for lung
dysfunction.[35]

Prognosis
EVD has a risk of death in those infected of between 25% and 90%.[1][145] As of September 2014, the
average risk of death among those infected is 50%.[1] The highest risk of death was 90% in the 2002–
2003 Republic of the Congo outbreak.[146] Early admission significantly increases survival rates [4]

Death, if it occurs, follows typically six to sixteen days after symptoms appear and is often due to low
blood pressure from fluid loss.[2] Early supportive care to prevent dehydration may reduce the risk of
death

Post-Ebola virus syndrome

If an infected person survives, recovery may be quick and complete.[25][147] However, a large portion
of survivors develop post-Ebola virus syndrome after the acute phase of the infection.[148]

Prolonged cases are often complicated by the occurrence of long-term problems, such as inflammation
of the testicles, joint pains, fatigue, hearing loss, mood and sleep disturbances, muscular pain,
abdominal pain, menstrual abnormalities, miscarriages, skin peeling, or hair loss.[25][147] Inflammation
and swelling of the uveal layer of the eye is the most common eye complication in survivors of Ebola
virus disease.[147] Eye symptoms, such as light sensitivity, excess tearing, and vision loss have been
described.[149]

Ebola can stay in some body parts like the eyes,[150] breasts, and testicles after infection.[6][151] Sexual
transmission after recovery has been suspected.[152][153] If sexual transmission occurs following
recovery it is believed to be a rare event.[154] One case of a condition similar to meningitis has been
reported many months after recovery, as of October 2015.[155]

Epidemiology

For more about specific outbreaks, see List of Ebola outbreaks.

The disease typically occurs in outbreaks in tropical regions of Sub-Saharan Africa.[1] From 1976 (when
it was first identified) through 2013, the WHO reported 2,387 confirmed cases with 1,590 overall
fatalities.[1][14] The largest outbreak to date was the Ebola virus epidemic in West Africa, which caused
a large number of deaths in Guinea, Sierra Leone, and Liberia.[16][17]

1976

Sudan
Cotton factory in Nzara, South Sudan, where the first outbreak occurred

The first known outbreak of EVD was identified only after the fact. It occurred between June and
November 1976, in Nzara, South Sudan[44][156] (then part of Sudan), and was caused by Sudan virus
(SUDV). The Sudan outbreak infected 284 people and killed 151. The first identifiable case in Sudan
occurred on 27 June in a storekeeper in a cotton factory in Nzara, who was hospitalised on 30 June and
died on 6 July.[35][157] Although the WHO medical staff involved in the Sudan outbreak knew that they
were dealing with a heretofore unknown disease, the actual "positive identification" process and the
naming of the virus did not occur until some months later in Zaire.[157]

Zaire

Main article: 1976 Zaire Ebola virus outbreak

A CDC worker incinerates medical waste from Ebola patients in Zaire in 1976.

On 26 August 1976, the second outbreak of EVD began in Yambuku, a small rural village in Mongala
District in northern Zaire (now known as the Democratic Republic of the Congo).[158][159] This
outbreak was caused by EBOV, formerly designated Zaire ebolavirus, a different member of the genus
Ebolavirus than in the first Sudan outbreak. The first person infected with the disease was the village
school's headmaster Mabalo Lokela, who began displaying symptoms on 26 August 1976.[160] Lokela
had returned from a trip to Northern Zaire near the border of the Central African Republic, after visiting
the Ebola River between 12 and 22 August. He was originally believed to have malaria and was given
quinine. However, his symptoms continued to worsen, and he was admitted to Yambuku Mission
Hospital on 5 September. Lokela died on 8 September 14 days after he began displaying symptoms.[161]
[162]

Soon after Lokela's death, others who had been in contact with him also died, and people in Yambuku
began to panic. The country's Minister of Health and Zaire President Mobutu Sese Seko declared the
entire region, including Yambuku and the country's capital, Kinshasa, a quarantine zone. No-one was
permitted to enter or leave the area, and roads, waterways, and airfields were placed under martial law.
Schools, businesses and social organisations were closed.[163] The initial response was led by Congolese
doctors, including Jean-Jacques Muyembe-Tamfum, one of the discoverers of Ebola. Muyembe took a
blood sample from a Belgian nun; this sample would eventually be used by Peter Piot to identify the
previously unknown Ebola virus.[164] Muyembe was also the first scientist to come into direct contact
with the disease and survive.[165] Researchers from the Centers for Disease Control and Prevention
(CDC), including Piot, co-discoverer of Ebola, later arrived to assess the effects of the outbreak,
observing that "the whole region was in panic."[166][167][168]

Piot concluded that Belgian nuns had inadvertently started the epidemic by giving unnecessary vitamin
injections to pregnant women without sterilizing the syringes and needles. The outbreak lasted 26 days
and the quarantine lasted two weeks. Researchers speculated that the disease disappeared due to the
precautions taken by locals, the quarantine of the area, and discontinuing of the injections.[163]

During this outbreak, Ngoy Mushola recorded the first clinical description of EVD in Yambuku, where he
wrote the following in his daily log: "The illness is characterised with a high temperature of about 39 °C
(102 °F), haematemesis, diarrhoea with blood, retrosternal abdominal pain, prostration with 'heavy'
articulations, and rapid evolution death after a mean of three days."[169]

The virus responsible for the initial outbreak, first thought to be the Marburg virus, was later identified
as a new type of virus related to the genus Marburgvirus. Virus strain samples isolated from both
outbreaks were named "Ebola virus" after the Ebola River, near the first-identified viral outbreak site in
Zaire.[35] Reports conflict about who initially coined the name: either Karl Johnson of the American CDC
team[170] or Belgian researchers.[171] Subsequently, a number of other cases were reported, almost all
centred on the Yambuku mission hospital or close contacts of another case.[160] In all, 318 cases and
280 deaths (an 88% fatality rate) occurred in Zaire.[172] Although the two outbreaks were at first
believed connected, scientists later realised that they were caused by two distinct ebolaviruses, SUDV
and EBOV

1995–2014

Cases of Ebola fever in Africa since 1976

The second major outbreak occurred in Zaire (now the Democratic Republic of the Congo, DRC), in 1995,
affecting 315 and killing 254.[1]

In 2000, Uganda had an outbreak infecting 425 and killing 224; in this case, the Sudan virus was found to
be the Ebola species responsible for the outbreak.[1]

In 2003, an outbreak in the DRC infected 143 and killed 128, a 90% death rate, the highest of a genus
Ebolavirus outbreak to date.[173]
In 2004, a Russian scientist died from Ebola after sticking herself with an infected needle.[174]

Between April and August 2007, a fever epidemic[175] in a four-village region[176] of the DRC was
confirmed in September to have been cases of Ebola.[177] Many people who attended the recent
funeral of a local village chief died.[176] The 2007 outbreak eventually infected 264 individuals and
killed 187.[1]

On 30 November 2007, the Uganda Ministry of Health confirmed an outbreak of Ebola in the
Bundibugyo District in Western Uganda. After confirming samples tested by the United States National
Reference Laboratories and the Centers for Disease Control, the World Health Organization (WHO)
confirmed the presence of a new species of genus Ebolavirus, which was tentatively named Bundibugyo.
[178] The WHO reported 149 cases of this new strain and 37 of those led to deaths.[1]

The WHO confirmed two small outbreaks in Uganda in 2012, both caused by the Sudan variant. The first
outbreak affected seven people, killing four, and the second affected 24, killing 17.[1]

On 17 August 2012, the Ministry of Health of the DRC reported an outbreak of the Ebola-Bundibugyo
variant[179] in the eastern region.[180][181] Other than its discovery in 2007, this was the only time
that this variant has been identified as responsible for an outbreak. The WHO revealed that the virus
had sickened 57 people and killed 29. The probable cause of the outbreak was tainted bush meat
hunted by local villagers around the towns of Isiro and Viadana.[1][182]

In 2014, an outbreak occurred in the DRC. Genome-sequencing showed that this outbreak was not
related to the 2014–15 West Africa Ebola virus outbreak, but was the same EBOV species, the Zaire
species.[183] It began in August 2014, and was declared over in November with 66 cases and 49 deaths.
[184] This was the 7th outbreak in the DRC, three of which occurred during the period when the country
was known as Zaire.[185]

2013–2016 West Africa

Main article: West African Ebola virus epidemic

Cases and deaths from April 2014 to July 2015 during the 2013–2015 outbreak

In March 2014, the World Health Organization (WHO) reported a major Ebola outbreak in Guinea, a
West African nation.[186] Researchers traced the outbreak to a one-year-old child who died in
December 2013.[187][188] The disease rapidly spread to the neighbouring countries of Liberia and
Sierra Leone. It was the largest Ebola outbreak ever documented, and the first recorded in the region.
[186] On 8 August 2014, the WHO declared the epidemic an international public health emergency.
Urging the world to offer aid to the affected regions, its Director-General said, "Countries affected to
date simply do not have the capacity to manage an outbreak of this size and complexity on their own. I
urge the international community to provide this support on the most urgent basis possible."[189] By
mid-August 2014, Doctors Without Borders reported the situation in Liberia's capital, Monrovia, was
"catastrophic" and "deteriorating daily". They reported that fears of Ebola among staff members and
patients had shut down much of the city's health system, leaving many people without medical
treatment for other conditions.[190] In a 26 September statement, WHO said, "The Ebola epidemic
ravaging parts of West Africa is the most severe acute public health emergency seen in modern times.
Never before in recorded history has a biosafety level four pathogen infected so many people so quickly,
over such a broad geographical area, for so long."[191]

Intense contact tracing and strict isolation largely prevented further spread of the disease in the
countries that had imported cases.

It caused significant mortality, with a considerable case fatality rate.[192][193][194][note 1] By the end
of the epidemic, 28,616 people had been infected; of these, 11,310 had died, for a case-fatality rate of
40%.[195] As of 8 May 2016, 28,646 suspected cases and 11,323 deaths were reported;[15][196]
however, the WHO said that these numbers may be underestimated.[197] Because they work closely
with the body fluids of infected patients, healthcare workers were especially vulnerable to infection; in
August 2014, the WHO reported that 10% of the dead were healthcare workers.[198]

2014 Ebola virus epidemic in West Africa

In September 2014, it was estimated that the countries' capacity for treating Ebola patients was
insufficient by the equivalent of 2,122 beds; by December there were a sufficient number of beds to
treat and isolate all reported Ebola cases, although the uneven distribution of cases was causing serious
shortfalls in some areas.[199] On 28 January 2015, the WHO reported that for the first time since the
week ending 29 June 2014, there had been fewer than 100 new confirmed cases reported in a week in
the three most-affected countries. The response to the epidemic then moved to a second phase, as the
focus shifted from slowing transmission to ending the epidemic.[200] On 8 April 2015, the WHO
reported only 30 confirmed cases, the lowest weekly total since the third week of May 2014.[201]

On 29 December 2015, 42 days after the last person tested negative for a second time, Guinea was
declared free of Ebola transmission.[202] At that time, a 90-day period of heightened surveillance was
announced by that agency. "This is the first time that all three countries – Guinea, Liberia and Sierra
Leone – have stopped the original chains of transmission ...", the organisation stated in a news release.
[203] A new case was detected in Sierra Leone on 14 January 2016.[204] However, the outbreak was
declared no longer an emergency on 29 March 2016.[18]

2014 spread outside West Africa

Main articles: Ebola virus cases in the United States, Ebola virus disease in Spain, and Ebola virus disease
in the United Kingdom

On 19 September, Eric Duncan flew from his native Liberia to Texas; five days later he began showing
symptoms and visited a hospital but was sent home. His condition worsened and he returned to the
hospital on 28 September, where he died on 8 October. Health officials confirmed a diagnosis of Ebola
on 30 September – the first case in the United States

In early October, Teresa Romero, a 44-year-old Spanish nurse, contracted Ebola after caring for a priest
who had been repatriated from West Africa. This was the first transmission of the virus to occur outside
Africa.[206] Romero tested negative for the disease on 20 October, suggesting that she may have
recovered from Ebola infection.[207]

On 12 October, the Centers for Disease Control and Prevention (CDC) confirmed that a nurse in Texas,
Nina Pham, who had treated Duncan tested positive for the Ebola virus, the first known case of
transmission in the United States.[208] On 15 October, a second Texas health-care worker who had
treated Duncan was confirmed to have the virus.[77][209] Both of these people recovered.[210] An
unrelated case involved a doctor in New York City, who returned to the United States from Guinea after
working with Médecins Sans Frontières and tested positive for Ebola on 23 October.[211] The person
recovered and was discharged from Bellevue Hospital on 11 November.[210] On 24 December 2014, a
laboratory in Atlanta, Georgia reported that a technician had been exposed to Ebola.[212]

On 29 December 2014, Pauline Cafferkey, a British nurse who had just returned to Glasgow from Sierra
Leone, was diagnosed with Ebola at Glasgow's Gartnavel General Hospital.[213] After initial treatment in
Glasgow, she was transferred by air to RAF Northolt, then to the specialist high-level isolation unit at the
Royal Free Hospital in London for longer-term treatment.[214]

2017 Democratic Republic of the Congo

Main article: 2017 Democratic Republic of the Congo Ebola virus outbreak

On 11 May 2017, the DRC Ministry of Public Health notified the WHO about an outbreak of Ebola. Four
people died, and four people survived; five of these eight cases were laboratory-confirmed. A total of
583 contacts were monitored. On 2 July 2017, the WHO declared the end of the outbreak.[215]

2018 Équateur province

Main article: 2018 Équateur province Ebola outbreak

On 14 May 2018, the World Health Organization reported that "the Democratic Republic of Congo
reported 39 suspected, probable or confirmed cases of Ebola between 4 April and 13 May, including 19
deaths."[216] Some 393 people identified as contacts of Ebola patients were being followed up. The
outbreak centred on the Bikoro, Iboko, and Wangata areas in Equateur province,[216] including in the
large city of Mbandaka. The DRC Ministry of Public Health approved the use of an experimental vaccine.
[217][218][219] On 13 May 2018, WHO Director-General Tedros Adhanom Ghebreyesus visited Bikoro.
[220] Reports emerged that maps of the area were inaccurate, not so much hampering medical
providers as epidemiologists and officials trying to assess the outbreak and containment efforts.[221]
The 2018 outbreak in the DRC was declared over on 24 July 2018.[22]

2018–2020 Kivu

Main article: Kivu Ebola epidemic

On 1 August 2018, the world's 10th Ebola outbreak was declared in North Kivu province of the
Democratic Republic of the Congo. It was the first Ebola outbreak in a military conflict zone, with
thousands of refugees in the area.[222][223] By November 2018, nearly 200 Congolese had died of
Ebola, about half of them from the city of Beni, where armed groups are fighting over the region's
mineral wealth, impeding medical relief efforts.[224]

By March 2019, this became the second largest Ebola outbreak ever recorded, with more than 1,000
cases and insecurity continuing to be the major resistance to providing an adequate response.[225][226]
As of 4 June 2019, the WHO reported 2025 confirmed and probable cases with 1357 deaths.[227] In
June 2019, two people died of Ebola in neighbouring Uganda.[228]
In July 2019, an infected man travelled to Goma, home to more than two million people.[229] One week
later, on 17 July 2019, the WHO declared the Ebola outbreak a global health emergency, the fifth time
such a declaration has been made by the organisation.[230] A government spokesman said that half of
the Ebola cases are unidentified, and he added that the current outbreak could last up to three years.
[231]

On 25 June 2020, the second biggest EVD outbreak ever was declared over.[232]

2020 Équateur province

On 1 June 2020, the Congolese health ministry announced a new DRC outbreak of Ebola in Mbandaka,
Équateur Province, a region along the Congo River. Genome sequencing suggests that this outbreak, the
11th outbreak since the virus was first discovered in the country in 1976, is unrelated to the one in
North Kivu Province or the previous outbreak in the same area in 2018. It was reported that six cases
had been identified; four of the people had died. It is expected that more people will be identified as
surveillance activities increase.[233] By 15 June the case count had increased to 17 with 11 deaths, with
more than 2,500 people having been vaccinated.[234] The 11th EVD outbreak was officially declared
over on 19 November 2020.[235] By the time the Équateur outbreak ended, it had 130 confirmed cases
with 75 recoveries and 55 deaths.

2021

North Kivu

On 7 February 2021, the Congolese health ministry announced a new case of Ebola near Butembo,
North Kivu detected a day before. The case was a 42-year-old woman who had symptoms of Ebola in
Biena on 1 February 2021. A few days after, she died in a hospital in Butembo. The WHO said that more
than 70 people with contact with the woman had been tracked.[236][237]

On 11 February 2021, another woman who had contact with the previous woman died in the same
town, and the number of traced contacts increased to 100.[238] A day after, a third case was detected in
Butembo.[239]

On 3 May 2021, the 12th EVD outbreak was declared over, resulting in 12 cases and six deaths.[240]
[241] Heightened surveillance will continue for 90 days after the declaration, in case of resurgence.[240]
Guinea

In February 2021, Sakoba Keita, head of Guinea's national health agency confirmed that three people
had died of Ebola in the south-eastern region near the city of Nzérékoré. A further five people also
tested positive. Keita also confirmed more testing was underway, and attempts to trace and isolate
further cases had begun.[242] On 14 February, the Guinean government declared an Ebola epidemic.
[243] The outbreak may have started following reactivation of a latent case in a survivor of an earlier
outbreak.[244][245] As of 4 May 2021, 23 cases were reported, with no new cases or deaths since 3
April 2021.[240] A 42-day countdown period was started on 8 May 2021, and on 19 June, the outbreak
was declared over.[240][246]

Ivory Coast

On 14 August 2021, The Ministry of Health of Cote d’Ivoire confirmed the country's first case of Ebola
since 1994. This came after the Institut Pasteur in Cote d'Ivoire confirmed the Ebola Virus Disease in
samples collected from a patient, who was hospitalized in the commercial capital of Abidjan, after
arriving from Guinea.[247]

However, on 31 August 2021, the WHO found that, after further tests in a laboratory in Lyon, the patient
did not have Ebola. The cause of her disease is still being analyzed.[248]

2022

On 23 April 2022, a case of Ebola was confirmed in the DRC in the Equateur province. The case was a 31-
year-old man whose symptoms began on 5 April, but did not seek treatment for over a week. On 21
April, he was admitted to an Ebola treatment centre and died later that day.[249] By 24 May 2022, there
were 5 recorded deaths in the DRC.[250] On 15 August, the fifth case was buried, and the outbreak was
declared over, 42 days after, on 4 July 2022.[251]

In September 2022, Uganda reported 7 cases infected with the Ebola Sudan strain,[252] but by mid-
October the count had increased to 63.[253] In November 2022, the outbreak in Uganda continued - still
without a vaccine.[4] On 10 January 2023, the outbreak was considered over after no new cases had
been reported for 42 days; the outbreak killed nearly 80 people.[254]

Society and culture

See also: Cultural effects of the Ebola crisis

Weaponisation

Ebolavirus is classified as a biosafety level 4 agent, as well as a Category A bioterrorism agent by the
Centers for Disease Control and Prevention.[96][255] It has the potential to be weaponised for use in
biological warfare,[256][257] and was investigated by Biopreparat for such use, but might be difficult to
prepare as a weapon of mass destruction because the virus becomes ineffective quickly in open air.[258]
Fake emails pretending to be Ebola information from the WHO or the Mexican government have, in
2014, been misused to spread computer malware.[259] The BBC reported in 2015 that "North Korean
state media has suggested the disease was created by the U.S. military as a biological weapon."[260]

Literature

Richard Preston's 1995 best-selling book, The Hot Zone, dramatised the Ebola outbreak in Reston,
Virginia.[261][262][263]

William Close's 1995 Ebola: A Documentary Novel of Its First Explosion[264][265] and 2002 Ebola:
Through the Eyes of the People focused on individuals' reactions to the 1976 Ebola outbreak in Zaire.
[266][267]

Tom Clancy's 1996 novel, Executive Orders, involves a Middle Eastern terrorist attack on the United
States using an airborne form of a deadly Ebola virus strain named "Ebola Mayinga" (see Mayinga
N'Seka).[268][269]

As the Ebola virus epidemic in West Africa developed in 2014, a number of popular self-published and
well-reviewed books containing sensational and misleading information about the disease appeared in
electronic and printed formats. The authors of some such books admitted that they lacked medical
credentials and were not technically qualified to give medical advice. The World Health Organization and
the United Nations stated that such misinformation had contributed to the spread of the disease.

Other animals

Wild animals

Ebola has a high mortality rate among primates.[271] Frequent outbreaks of Ebola may have resulted in
the deaths of 5,000 gorillas.[272] Outbreaks of Ebola may have been responsible for an 88% decline in
tracking indices of observed chimpanzee populations in the 420 km2 Lossi Sanctuary between 2002 and
2003.[273] Transmission among chimpanzees through meat consumption constitutes a significant risk
factor, whereas contact between the animals, such as touching dead bodies and grooming, is not.[274]
Recovered gorilla carcasses have contained multiple Ebola virus strains, suggesting multiple
introductions of the virus. Bodies decompose quickly and carcasses are not infectious after three to four
days. Contact between gorilla groups is rare, suggesting that transmission among gorilla groups is
unlikely, and that outbreaks result from transmission between viral reservoirs and animal populations.
[273]

Domestic animals

In 2012, it was demonstrated that the virus can travel without contact from pigs to nonhuman primates,
although the same study failed to achieve transmission in that manner between primates.[86][275]

Dogs may become infected with EBOV but not develop symptoms. Dogs in some parts of Africa scavenge
for food, and they sometimes eat EBOV-infected animals and also the corpses of humans. A 2005 survey
of dogs during an EBOV outbreak found that although they remain asymptomatic, about 32 percent of
dogs closest to an outbreak showed a seroprevalence for EBOV versus nine percent of those farther
away.[276] The authors concluded that there were "potential implications for preventing and controlling
human outbreaks."

Reston virus

For more about the outbreak in Virginia, US, see Reston virus.

In late 1989, Hazelton Research Products' Reston Quarantine Unit in Reston, Virginia, had an outbreak of
fatal illness amongst certain lab monkeys. This lab outbreak was initially diagnosed as simian
haemorrhagic fever virus (SHFV) and occurred amongst a shipment of crab-eating macaque monkeys
imported from the Philippines. Hazelton's veterinary pathologist in Reston sent tissue samples from
dead animals to the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) at
Fort Detrick, Maryland, where an ELISA test indicated the antibodies present in the tissue were a
response to Ebola virus and not SHFV.[277] An electron microscopist from USAMRIID discovered
filoviruses similar in appearance, in crystalloid aggregates and as single filaments with a shepherd's
hook, to Ebola in the tissue samples sent from Hazelton Research Products' Reston Quarantine Unit.
[278]

A US Army team headquartered at USAMRIID euthanised the surviving monkeys, and brought all the
dead monkeys to Fort Detrick for study by the Army's veterinary pathologists and virologists, and
eventual disposal under safe conditions.[277] Blood samples were taken from 178 animal handlers
during the incident.[279] Of those, six animal handlers eventually seroconverted, including one who had
cut himself with a bloody scalpel.[97][280] Despite its status as a Level-4 organism and its apparent
pathogenicity in monkeys, when the handlers did not become ill, the CDC concluded that the virus had a
very low pathogenicity to humans.[280][281]

The Philippines and the United States had no previous cases of Ebola infection, and upon further
isolation, researchers concluded it was another strain of Ebola, or a new filovirus of Asian origin, which
they named Reston ebolavirus (RESTV) after the location of the incident.[277] Reston virus (RESTV) can
be transmitted to pigs.[86] Since the initial outbreak it has since been found in nonhuman primates in
Pennsylvania, Texas, and Italy,[282] where the virus had infected pigs.[283] According to the WHO,
routine cleaning and disinfection of pig (or monkey) farms with sodium hypochlorite or detergents
should be effective in inactivating the Reston ebolavirus. Pigs that have been infected with RESTV tend
to show symptoms of the disease.

Research

Treatments

Main article: Ebola virus disease treatment research

Researchers looking at slides of cultures of cells that make monoclonal antibodies. These are grown in a
lab and the researchers are analyzing the products to select the most promising.

As of July 2015, no medication has been proven safe and effective for treating Ebola. By the time the
Ebola virus epidemic in West Africa began in 2013, there were at least nine different candidate
treatments. Several trials were conducted in late 2014, and early 2015, but some were abandoned due
to lack of efficacy or lack of people to study.[285]

As of August 2019, two experimental treatments known as atoltivimab/maftivimab/odesivimab and

ansuvimab were found to be 90% effective.[286][287][288]

Diagnostic tests

The diagnostic tests currently available require specialised equipment and highly trained personnel.
Since there are few suitable testing centres in West Africa, this leads to delay in diagnosis.[289]
On 29 November 2014, a new 15-minute Ebola test was reported that if successful, "not only gives
patients a better chance of survival, but it prevents transmission of the virus to other people." The new
equipment, about the size of a laptop and solar-powered, allows testing to be done in remote areas.
[290]

On 29 December 2014, the U.S. Food and Drug Administration (FDA) approved the LightMix Ebola Zaire
rRT-PCR test for patients with symptoms of Ebola.[291]

Disease models

Animal models and in particular non-human primates are being used to study different aspects of Ebola
virus disease. Developments in organ-on-a-chip technology have led to a chip-based model for Ebola
haemorrhagic syndrome