FAMILY corOnavirIDAE
KIUT
BMLS 2
By
Mwamkoa, M.J.
Introduction
• The coronaviridae family includes several types of viruses that
can infect vertebrates including dogs, cats, cattle, pigs,
rodents and poultry.
• There are two genera in the Coronaviridae family:
– Coronavirus and
– Torovirus
• The toroviruses are widespread in ungulates and appear to be
associated with diarrheas.
Coronavirus
• The name Coronavirus is derived from Latin corona meaning
crown or halo (royal crown-like appearance)
• It refers to the characteristic appearance of virion under
electron microscopy
• Coronaviruses are large, enveloped RNA viruses.
• The viruses cause respiratory tract infections that can range
from mild to lethal.
• Mild illnesses include some cases of the common cold and more
lethal varieties i.e. SARS, MERS, and COVID-19.
Coronavirus…
• The human coronaviruses have also implicated in gastroenteritis
in infants.
• Animal coronaviruses cause diseases of economic importance in
domestic animals.
Pathogenic strains of Coronavirus
• The human pathogens includes;
– Human coronavirus 229E (alpha Corona virus).
– Human coronavirus OC43 (beta coronavirus)
– SARS-Cov (Severe Acute Respiratory Syndrome)
– Human coronavirus HKU1
– MERS-coronavirus (Middle East Respiratory Syndrome)
– Human coronavirus NL63 (alpha Corona virus).
– SARS-CoV-2 - causes COVID-19, the respiratory illness.
Antigenic and genomic structure
• Two serogroups of human coronaviruses, represented by
strains 229E and OC43.
• SARS-CoV;
– Genomic sequence differ from other coronavirus strains.
– Are relatively stable compared to other coronaviruses
– Found in group 2 (OC43).
• Coronaviruses of domestic animals and rodents are included in
these two groups.
Morphology of Coronaviruses
• Are enveloped, nonsegmented, ss (+) RNA virus (30 kb in length).
• The virus contains the glycoproteins E1 and E2 and a core
nucleoprotein N.
• The glycoproteins appear as club-shaped projections (20 nm long and
5–11 nm wide) on surface of the envelope.
– E1 – a transmembrane matrix protein
– E2 - mediates viral attachment and membrane fusion.
– N protein - forms a helical nucleocapsid.
– E3 - a hemagglutinin neuraminidase/Hemagglutinin esterase (HE) found in
some strains (B-corona virus subgroup A).
Epidemiology
• The SARS outbreak in 2002–2003 predominantly affected
mainland China, Hong Kong, Singapore, Taiwan, and Canada.
• The SARS strain is believed to have originated in the southern
Chinese city of Guangzhou (Guangdong province).
• The disease is epidemiologically linked to the National Institute
of Virology in Beijing, where the outbreak is thought to have
originated.
• A total of 8098 cases, 774 deaths, and 7324 recoveries from
SARS were documented between Nov, 2002 and April 21, 2004.
Epidemiology…
• SARS-CoV-2 – the current outbreak of coronavirus disease
(COVID-19).
• First reported from Wuhan, China, on 31 December 2019.
• From China it spread worldwide and was declared as pandemic
in 2020.
• On 11 February 2020, the International Committee on
Taxonomy of Viruses adopted the official name "SARS-CoV-2”.
Epidemiology…
• Globally until 19th July 2021, there are 191 million cases of
COVID-19 and with more than 4.09 million deaths reported to
WHO, making it one of the deadliest pandemic in history.
SARS-CoV-2 Variants
• SARS-CoV-2 continuously change in their genetic code (caused
by genetic mutations or viral recombination).
• This occur during replication of the genome.
• Most changes have little to no impact on the virus’ properties.
• However, some changes may affect the virus’s properties, such
as how easily it spreads, the associated disease severity, or
the performance of vaccines, therapeutic medicines, diagnostic
tools, or other public health and social measures.
SARS-CoV-2 Variants…
• A variant has one or more mutations that differentiate it from
other variants of the SARS-CoV-2 viruses.
• Multiple variants of SARS-CoV-2 have been documented
globally throughout this pandemic.
SARS-CoV-2 Variants…
Year and
Country first Impact on Impact on
WHO label month first
detected transmissibility severity
detected
United
Alpha Sep-2020 Increased Increased
Kingdom
Beta South Africa Sep-2020 Increased Increased
Gamma Brazil Dec-2020 Increased Increased
Delta India Dec-2020 Increased Increased
South Africa
Omicron Nov-2021 Increased Reduced
and Botswana
Reservoir, source and transmission of infection
• There is likelihood that, Coronavirus originated in a nonhuman
host and acquired the ability to infect humans.
• Chinese horseshoe bats are natural reservoirs of SARS-like
coronaviruses.
• In rural regions of southern China, where the outbreak began,
people, pigs, and domestic fowl live close together and there is
widespread use of wild species for food and traditional
medicine—conditions that promote the emergence of new viral
strains.
Reservoir, source and transmission of infection…
• Primary transmission is by close person-to-person contact.
• The infection is acquired by;
– inhalation of infectious droplets during the act of coughing or
sneezing, from infected individual.
– direct contact of the eyes, nose, or mouth of susceptible
individuals with infectious secretions of infected individual.
Transmission…
• WHO categorized the COVID-19 transmission in three
phases;
– Symptomatic transmission,
– Pre-symptomatic transmission and
– Asymptomatic transmission
WHO Coronavirus disease 2019 (COVID-19) Situation Report – 73
Symptomatic transmission
• Transmission from an individual with COVID-19 virus infection and
experiencing symptoms.
• Can be transmitted to people who are in close contact through respiratory
droplets, by direct contact with infected persons, or by contact with
contaminated objects and surfaces.
• Early in the course of the disease viruses are highest shed from upper
respiratory tract (nose and throat) .
• That is, within the first 3 days from onset of symptoms.
• People may be more contagious around the time of symptom onset as
compared to later on in the disease
WHO Coronavirus disease 2019 (COVID-19) Situation Report – 73
Pre-Symptomatic transmission
Pre-symptomatic transmission
• The incubation period for COVID-19, is on average 5-6 days,
however can be up to 14 days.
• During this period, also known as the “presymptomatic” period,
some infected persons can be contagious.
• Some people can test positive for COVID-19 from 1-3 days
before they develop symptoms.
WHO Coronavirus disease 2019 (COVID-19) Situation Report – 73
Transmission…
• Asymptomatic transmission;
– A laboratory-confirmed case infected with COVID-19 who does
not develop symptoms.
• Transmission due to asymptomatic infection is not entirely
clear.
• However, recent studies suggest that people who are not
showing symptoms may transmit the virus
CDC February 2021
Viral Replication
Pathogenesis
• Coronaviruses tend to be highly species-specific.
• Display a tropism for epithelial cells of the respiratory or
gastrointestinal tract.
• The virus attaches to receptors on target cells by the
glycoprotein spikes on the viral envelope (either by S or HE).
• The receptor for human coronavirus 229E is aminopeptidase N,
whereas a functional receptor for the SARS virus is
angiotensin-converting enzyme 2 (ACE-2).
Clinical Features
• The human coronaviruses produce "colds," usually afebrile, in
adults.
• The symptoms are similar to those produced by rhinoviruses,
typified by nasal discharge and malaise.
• The incubation period is from 2 to 6 days or up to 14 days, and
symptoms usually last about 1 week.
• The lower respiratory tract is seldom involved.
• Asthmatic children may suffer wheezing attacks, and chronic
pulmonary disease in adults may exacerbate respiratory symptoms.
Clinical Features…
• The coronavirus causes severe respiratory disease.
• Common early symptoms include fever, malaise, chills, headache,
dizziness, cough, fatigue, loss of taste (ageusia) or smell
(anosmia), congestion or runny nose and sore throat, followed a
few days later by shortness of breath or difficulty breathing.
• Less common symptoms include aches and pains, diarrhea, nausea
or vomiting, conjunctivitis, rashes on skin, or discolouration of
fingers or toes.
• Many patients have abnormal chest radiographs.
Clinical Features…
• Some cases progress rapidly to acute respiratory distress,
requiring ventilatory support.
• In these cases there is alteration in fluid balance which leads
to development of edema in alveolar space.
• Diffuse edema resulting in hypoxia a characteristic of
pneumonia.
• Death from progressive respiratory failure occurs in almost
10% of cases, with the death rate highest among the elderly.
Clinical Features…
• Clinical features of coronavirus-associated enteritis have not
been clearly described. They appear to be similar to those of
rotavirus infections.
• Patients with older age and comorbidities are at increased risk
of developing severe COVID-19 illness
Immunity
• The immunity conferred by infection, apparently IgA-
dependent, is short lived.
• Reinfections are therefore frequent, whereby the antigenic
variability of the virus may be a contributing factor.
Diagnosis
• The common-cold coronavirus can be grown in organ cultures of
human tracheal tissue or in human diploid cells.
• Isolating the viruses for diagnostic purposes is not routine.
• Serology (complement-binding reaction, immunofluorescence
or enzyme immunoassay)
• Electron microscopy are feasible methods.
• PCR
• X-ray imaging
Prevention
• Protect yourself and others around you by knowing the facts and
taking appropriate precautions.
• To prevent the spread of COVID-19 and other Coronaviruses:
– Clean your hands often using soap and running water, or an alcohol-
based hand rub.
– Maintain a safe distance from anyone who is coughing or sneezing.
– Avoid unnecessary touching of eyes, nose or mouth.
– Cover your nose and mouth with your bent elbow or a tissue when you
cough or sneeze.
Prevention
– Use of masks
– Airport screeningfor potentially sick and/or febrile passengers.
– Isolation of patients, quarantine of those who had been exposed,
and travel restrictions
– Use of gloves, gowns, goggles, and respirators by health care
workers.
– Early seeking medical attention whenever you feel any related
symptoms.
– Follow advice provided by your local public health authority.
Management
• No specific treatment but you can use Ibuprofen or
acetaminophen to relief symptoms
• Administration of remdesivir (Veklury) in certain situations
• Take over the counter medicine for sore throat and fever, But
don’t give Aspirin to children since it may cause Reye syndrome
(damages in Liver and Brain).
• Patients with respiratory failure can be provided with
supportive care including oxygen or more advanced respiratory
support such as ventilation.
