Virology Phospolipid Bilayer

• A type of membrane that separates the cell from the

• the scientific discipline concerned with the study of the biology environment and is made of two layers of phospholipids.
of viruses and viral diseases, including the distribution,
biochemistry, physiology, molecular biology, ecology, evolution • sometimes called as Lipid Bilayer
and clinical aspects of viruses.
• The phospolipid bilayer in which the cell membrane
• It is a subfield of microbiology that focuses on their detection, surrounds the cell and forms a flexible barrier that
structure, classification and evolution, their methods of infection allows the cell to be separate from the extracellular space.
and exploitation of host cells for reproduction, their interaction
• A thin polar membrane made of two layers of lipid
with host organism physiology and immunity, the diseases they
molecules.
cause, the techniques to isolate and culture them, and their use
in research and therapy.

Virus CELL INTERACTIONS

• infect humans, lower animals, insects, plants, bacteria, and Intracellular

fungi. • Existing, occurring, or functioning within a cell

• Classification and nomenclature are standardized by the • Occurring or being (situated) inside a cell or cells.
International Committee on Taxonomy of Viruses through reports
• It is relating to, involving, or occurring in the space between
published periodically.
the cells of a multicellular organism or in the space between
cells of closely associated unicellular microorganisms such as
• divided into genera and species, as are bacteria, however, most
bacteria
are referred to by common names that have been used for
decades.

• are composed of a nucleic acid genome surrounded by a

protein coat called a capsid.

• Together the genome and capsid are referred to as the

nucleocapsid.

• Genomes are either RNA or DNA.

• are strict intracellular organisms, reproducing or replicating Intercellular

only within a host cell.
-it is L to, involving, or occuring in the space between the
• The steps in virus replication, called the infectious cycle, cells of a multicellular organism or in the space between cells
include attachment, penetration, uncoating, of closely associated unicellular microorganisms such as
macromolecular synthesis, assembly, and release. bacteria.

• To initiate the infectious cycle, a virus must first recognize

and bind to a suitable host cell, referred to
as attachment.

• They cannot replicate alone, instead, it must infect cells and

use components of the host cell to make copies of itself.

• Often, a virus ends up killing the host cell in the process,

causing damage to the host organism.

STRUCTURE OF A VIRUS

Capsid
• The protein shell of a virus, enclosing its genetic material.
• It consists of several oligomeric (repeating) structural subunits
made of protein called protomers.

Lipid Envelope
• Defined as a phospholipid bilayer resembling a cellular
membrane, consisting of host-derived lipids and virally coded
proteins, particularly integral glycoproteins crucial for virus-host
interactions.

• are acquired by enveloped viruses as they exit the host cell.

• Also called Viral Envelope.
• The outermost layer of many types of viruses.
 MERS-Cov
Respiratory Viruses • fever, cough and shortness of breath. Pneumonia is a
• are a group of viruses that infect the respiratory tract, common finding, but not always present. Gastrointestinal
causing illnesses ranging from mild colds to serious symptoms, including diarrhea
pneumonia
• acute upper respiratory illness, and rapidly progressive
Family pneumonitis, respiratory failure, septic shock and multi-organ
failure resulting in death

Coronaviridae
• Enveloped, Spherical, helical nucleocapsid
• club-shaped or petal shaped projections on their surfaces
• Transmission: respiratory
• ssRNA virus COVID-19
• 5 days after symptom onset is the recommended isolation
period

Severe Acute Respiratory Syndrome (SARS-Cov) Orthomyxoviridae

• Transmission: close person-to-person contact (within 3 feet), • Influenza viruses
respiratory droplets (droplet spread), air (airborne spread). • Helical, enveloped, segmented

• Highest in concentration: nasal passages: nasal epithelial cells • Stomach flu, also known as the 24-hour flu, is caused by
• high fever, dry cough, dyspnea viruses other than influenza viruses.

• An ssRNA virus
 4. Respiratory Syncytial Virus (RSV) (Paramyxoviridae)
• a common respiratory pathogen, particularly in infants and
young children, causing bronchiolitis and pneumonia, and can
Paramyxoviridae also affect adults, especially the elderly and
• respiratory infections of infants and young children immunocompromised.
(respiratory syncytial virus and the parainfluenza viruses) as
well as the causative agents of two of the most common • a leading and common cause of bronchiolitis and pneumonia,
contagious diseases of childhood (mumps and measles). especially in infants.
• Replication of the respiratory pathogens is limited to the • a common human pathogen, infecting nearly all children by
respiratory epithelia, whereas measles and mumps become age 2.
disseminated throughout the body and produce generalized
disease. • Reinfection is common throughout life, but infants and the
elderly remain at risk for symptomatic infection.
• a ssRNA virus
• Presents severe respiratory distress, especially in infants.

5. Parainfluenza Viruses (Paramyxoviridae)

• are single-stranded, negative-sense RNA viruses that cause
respiratory infections, particularly in young children, and can
range from mild to severe illness.

• Transmission: Primarily through respiratory droplets and

close contact.

Common Respiratory Viruses • This includes illnesses like colds, croup, bronchiolitis,
-Rhinoviruses (Picornaviridae) bronchitis and pneumonia.
-Influenza Viruses (Orthomyxoviridae)
• Also called as Human Parainfluenza Viruses (HPIVs)
-Respiratory Syncytial Virus (RSV) (Paramyxoviridae)
-Parainfluenza Viruses (Paramyxoviridae)
-Metapneumovirus (Paramyxoviridae)
-Coronaviruses (Coronaviridae)
-Adenoviruses
-Bocaviruses
6. Metapneumovirus (Paramyxoviridae)
• most commonly spread from person to person through
1. Rhinoviruses (Picornaviridae)
close contact with someone who is infected via
• The most frequent cause of the common cold and are a
secretions from coughing and sneezing or touching objects
common viral trigger for asthma attacks.
such as toys or doorknobs that have the virus on them.
• Most rhinovirus infections cause no symptoms or mild
• can cause upper (affecting the nose and throat) and lower
symptoms.
(affecting the lungs and airways) respiratory disease in
patients of all ages.
• They can also cause severe illness, especially if you have a
weakened immune system, asthma, or another underlying
• Also termed as Human Metapneumovirus (HMPV) ✓
medical condition. ^ VI
• You may have no signs or symptoms when you are infected
with a rhinovirus. C

7. Adenoviruses
2. Influenza Viruses (Orthomyxoviridae) • are a group of common viruses that can cause a range of
• Causes Flu, also called influenza, is an infection of the nose, illnesses.
throat and lungs, which are part of the respiratory system.
• They can also lead to other conditions, including
• can lead to mild to severe symptoms and, in some cases, conjunctivitis (pink eye), gastroenteritis (inflammation of the
death. stomach and intestines) and, less commonly, bladder
infections or neurological diseases.
• It spreads through the air via coughs or sneezes, or through
contact with infected surfaces. • Adenoviruses can affect people of all ages, but they are
particularly common in children.
3. Influenza Viruses (Orthomyxoviridae)
• There are three types of influenza viruses: A, B, and C. 8. Bocaviruses
• are a group of viruses in the Parvoviridae family.
• Presents a flu-like illness with severe muscle aches • infections are most common in young children.

• A Rapid influenza diagnostic test is performed first in patients • Bocavirus is often found in conjunction with other viral or
with a fever, cough, and confusion during flu season. bacterial infections, which can make it difficult to determine
its precise role in causing illness.
• Also termed as Human Bocavirus.
SIGNS & SYMPTOMS OF VIRAL RESPIRATORY INFECTION Gastrointestinal Viruses
• Norovirus
Dyspnea • Rotavirus
• Feeling of shortness of breath. • Astrovirus

Norovirus
• a common and very contagious virus.
• It causes nausea, severe vomiting, abdominal cramps,
low-grade fever and severe watery diarrhea.
Gastrointestinal Viruses
• Your symptoms may be similar to the stomach flu, but
they have a different cause.
Viral Gastroenteritis
• an intestinal infection that includes signs and symptoms such • Norovirus spreads easily through close contact or on
as watery diarrhea, stomach cramps, nausea or vomiting, and contaminated food or surfaces.
sometimes fever. • Most common cause of viral gastroenteritis worldwide.
• Most frequently linked to outbreaks of gastroenteritis on
• The most common way to develop viral gastroenteritis — cruise ships
often called stomach flu — is through contact with an infected
• Responsible for causing "winter vomiting disease“
person or by consuming contaminated food or water.
• Primary mode of transmission: Fecal-Oral Route
• Commonly implicated in foodborne gastroenteritis
• If you're otherwise healthy, you'll likely recover without
outbreaks linked to contaminated shellfish
complications.
• The illness runs its course in a few days.
• But for infants, older adults and people with compromised • Strict hand hygiene and environmental cleaning is the
immune systems, viral gastroenteritis can be deadly. most effective way to prevent the spread
• The leading cause of acute gastroenteritis.
• There's no effective treatment for viral gastroenteritis, so
prevention is key.
Rotavirus
• A very contagious virus that causes severe and watery
• Avoid food and water that may be contaminated and wash
diarrhea, vomiting and dehydration during the
your hands thoroughly and often.
winter months, it severely affects infants and young
children.
• Although it's commonly called stomach flu, gastroenteritis isn't
the same as influenza. • Before the development of a vaccine, most children had
been infected with the virus at least once by
• The flu (influenza) affects only your respiratory system — your age 5-6.
nose, throat and lungs.
• Although rotavirus infections are unpleasant, you can
• Supportive care, including rehydration is the primary treatment. usually treat this infection at home with extra fluids to
prevent dehydration.
• Gastroenteritis, on the other hand, attacks your intestines. • Occasionally, severe dehydration requires receiving fluids
• Depending on the cause, viral gastroenteritis symptoms may through a vein (intravenously) in the hospital.
appear within 1-3 days after you're infected and can range from
mild to severe. • Has a double-stranded RNA genome
• Vaccination can reduced severity and duration of rotavirus
• For viral gastroenteritis, treatment focuses on managing gastroenteritis.
symptoms and preventing dehydration, typically involving rest,
oral rehydration, and potentially anti-nausea or anti-diarrheal • Good hygiene, such as washing your hands regularly, is
medications, but antibiotics are ineffective. important.
• Preventable with a vaccine commonly administered to
infants
Symptoms • Presents severe watery diarrhea for 24 hours, acute
vomiting, and dehydration.
• Watery, usually nonbloody diarrhea — bloody diarrhea usually
means you have a different, more severe infection • Vaccination is the best way to prevent rotavirus infection.
• A rotavirus infection usually starts within two days of
• Nausea, vomiting or both exposure to the virus.
• Stomach cramps and pain
• Occasional muscle aches or headache • Strict handwashing and disinfection of contaminated
surfaces is the most effective preventive measure against
Rotavirus transmission in this setting.

• Vaccinated infants will experience a milder and shorter

duration of illness.
• Symptoms usually begin about 2 days after you come into
contact with the virus and last for 3 to 8 days.

• Most common in children.

Rotavirus Vaccine Adenovirus
• A vaccine used to protect against rotavirus infections, which • Researchers have identified about 50 types of
are the leading cause of severe diarrhea among young children. adenoviruses that can infect humans.

• Adenovirus infections occur throughout the year, but they

Astrovirus tend to peak in the winter and early spring.

• a common cause of mild diarrhea, vomiting and low-grade • Infections range from mild to severe, but serious illness
fever in kids. doesn’t happen often.
• Adults over 65 and people with weakened immune systems
can also get it. • Adenoviruses can affect people of all ages.
• It’s usually mild and goes away on its own in a few days. • But they’re most common in children younger than 5 years
• You can treat yourself at home by drinking plenty of fluids to old.
stay hydrated. • A patient with a weakened immune system develops
persistent diarrhea and abdominal pain.

Unusual Viruses That Causes Gastroenteritis

3. Hepatitis
1. HIV (human immunodeficiency virus) • an inflammation of the liver that is caused by a variety of
• A virus that attacks cells that help the body fight infection, infectious viruses and noninfectious agents leading to a
making a person more vulnerable to other infections and range of health problems, some of which can be fatal.
diseases.
• There are five main strains of the hepatitis virus, referred to
• May sometimes cause sudden-onset vomiting, diarrhea and as types A, B, C, D and E.
abdominal cramps.
• While they all cause liver disease, they differ in important
• It is spread by contact with certain bodily fluids of a person ways including modes of transmission, severity of the illness,
with HIV, most commonly during unprotected sex (sex without a geographical distribution and prevention methods.
condom or HIV medicine to prevent or treat HIV), or through
sharing injection drug equipment. • In particular, types B and C lead to chronic disease in
hundreds of millions of people and together are the most
• If left untreated, HIV can lead to the disease AIDS (acquired common cause of liver cirrhosis, liver cancer and viral
immunodeficiency syndrome). hepatitis-related deaths.

• Without treatment using HIV medicines, HIV infection advances • An estimated 354 million people worldwide live with
in stages, getting worse over time. hepatitis B or C, and for most, testing and treatment remain
beyond reach.

• Some types of hepatitis are preventable through

vaccination. Zz

• A WHO study found that an estimated 4.5 million

premature deaths could be prevented in low- and middle-
income countries by 2030 through vaccination, diagnostic
tests, medicines and education campaigns.

4. Hepatitis A Virus (HAV)

• An inflammation of the liver that can cause mild to severe
illness.

• Presents with jaundice, fever, and abdominal pain

• Transmitted through ingestion of contaminated food and

water or through direct contact with an infectious person.
2. Adenovirus
• are a group of viruses that can cause mild to severe infection
throughout your body. • Almost everyone recovers fully from hepatitis A with a
• Adenovirus infections most commonly affect your respiratory lifelong immunity.
system.
• These infections can cause symptoms similar to the common • However, a very small proportion of people infected with
cold or flu. hepatitis A could die from fulminant (severe & sudden in
• Most adenovirus infections are mild and require only symptom onset) hepatitis.
relief for treatment.
• has an available vaccine for prevention
• Commonly associated with gastroenteritis in • Common in a region with poor sanitation
immunocompromised patients
• Infection presents with fever, nausea, and jaundice
• Can cause gastrointestinal symptoms along with respiratory
illness

• Adenovirus is a common virus that can cause a range of cold- or

flu-like infections.
• Presents prolonged-diarrhea

• DNA virus
 5. Hepatitis B (HBV)
• a serious liver infection caused by the hepatitis B virus (HBV). • The virus is transmitted via the fecal-oral route, principally via
• For most people, hepatitis B is short term, also called acute. contaminated water.
• Acute hepatitis B lasts less than six months.
• known to cause the most severe complications during
• But for others, the infection lasts more than six months and pregnancy.
is called chronic.
• HEV caused 3450 deaths and there were an estimated 19.47
• Chronic hepatitis B raises the risk of liver failure, liver cancer million cases of acute hepatitis E (AHE)
and cirrhosis (serious scarring of the liver). globally in 2021.

• Most adults with hepatitis B recover fully, even if their

symptoms are bad.
• DNA virus

• HbsAg is a serological marker that indicates acute Hepatitis

B infection.

• Anti-Hbs is the marker that confirms immunity after Hepatitis

B vaccination.
• Active Hepatitis B infection with high infectivity presents 8. Herpesviridae
with fatigue, jaundice, and dark urine, and also, test shows • Orthoherpesviridae, previously named and more widely known
positive HBsAg and HBeAg. as Herpesviridae, is a large family of DNA viruses that cause
infections and certain diseases in animals, including humans.
• Administer HBIG and start the vaccination series if
unvaccinated if a needle stick happens if the patient is known • The members of this family are commonly known as
to have chronic Hepatitis B. herpesviruses.
• Has 2 types, the Acute or Short-term infection (6 months) &
the Chronic or Long-term Infection (more than 6 months). • The family name is derived from the Greek word ἕρπειν
(herpein 'to creep'), referring to spreading cutaneous lesions,
usually involving blisters, seen in flares of herpes simplex 1,
6. Hepatitis C (HCV)
herpes simplex 2 and herpes zoster (shingles).
• a virus that can infect the liver.
• If left untreated, it can sometimes cause serious and • In 1971, the International Committee on the Taxonomy of
potentially life-threatening damage to the liver over many Viruses (ICTV) established Herpesvirus as a genus with 23
years. viruses among four groups.
• But with modern treatments, it's usually possible to cure the • Since then, the number of identified herpesviruses has
infection, and most people with it will have a normal life grown to more than 100.
expectancy.
• It's estimated around 118,000 people in the UK had chronic • Herpesviruses can cause both latent and lytic infections.
hepatitis C in 2019. • Nine herpesvirus types are known to primarily infect humans,
• Has the highest risk of chronic infection at least five of which are extremely widespread among most
• Bloodborne is the most common route human populations, and which cause common diseases:
• often asymptomatic but can still result in long-term liver herpes simplex 1 and 2 (HSV-1 and HSV-2, also known as
damage HHV-1 and HHV-2; both of which can cause orolabial and
• Chronic Hepatitis C infection result shows HCV RNA positive genital herpes), varicella zoster (VZV or HHV-3; the cause of
but no detectable HBsAg or anti-HAV IgM. chickenpox and shingles), Epstein–Barr (EBV or HHV-4;
implicated in several diseases, including mononucleosis and
7. Hepatitis D (HDV) some cancers), and human cytomegalovirus (HCMV or HHV-5).
• a liver disease caused by the hepatitis D virus (HDV).
• Only people with hepatitis B can contract HDV. • An estimated 3.8 billion people under age 50 (64%) globally
• Hepatitis B vaccination provides protection against hepatitis B have herpes simplex virus type 1 (HSV-1) infection, the main
and, therefore, against hepatitis D. cause of oral herpes.

• People with hepatitis D show severe symptoms of the disease • causes oral herpes, genital herpes and infections in other
areas of your body.

• Fluid-filled blisters on your skin are common symptoms, but

many people have no symptoms at all.
Hepatitis E (HEV)
• an inflammation of the liver caused by infection with the • Acyclovir is an antiviral medication that is commonly used to
hepatitis E virus (HEV). treat herpes infections

• Every year there are an estimated 20 million HEV infections • A patient infected with this develops a painful, localized skin
worldwide, leading to an estimated 3.3 million symptomatic lesion with vesicles.
cases of hepatitis E.
• Causes a latent infection in nerve ganglia
• WHO estimates that hepatitis E caused approximately 44 000
deaths in 2015 (accounting for 3.3% of the mortality due to viral
hepatitis).
 HerpeSVIRIDAE
human herpesvirus 6
1. herpes simplex virus type 1
• Though the most common manifestation of human
2. herpes simplex virus type 2
herpesvirus 6 (HHV-6) is the rash exanthema subitum, also
3. varicella-zoster virus
called roseola + infantum, HHV-6 has been known to establish a
4. Cytomegalovirus
more threatening infection in immunocompromised individuals.
5. Epstein-Barr virus
6. human herpesvirus 6
• Interprofessional team members should recognize that further
7. human herpesvirus 7
evaluation for this condition is warranted when an
8. Kaposi's Sarcoma herpesvirus.
immunocompromised patient presents with behavior changes
with or without a rash.
herpes simplex virus type 1
• Type 1 (HSV-1) mostly spreads by oral contact and causes • responsible for roseola in infants
infections in or around the mouth (oral herpes or cold sores).

• remains dormant in the trigeminal ganglion after primary

infection
human herpesvirus 7
• a type of virus that typically causes a mild and self-limited
herpes simplex virus type 2 infection in children, with rare complications that may involve
• Type 2 (HSV-2) spreads by sexual contact and causes genital the central nervous system
herpes
• It has been associated with skin conditions like pityriasis
• Primary mode of transmission is sexual contact. rosea and can be transmitted through saliva.

varicella-zoster virus (VZV)

• an alpha herpes virus that causes chickenpox, herpes zoster Kaposi's Sarcoma-Associated herpesvirus (KSHV)
(shingles) and other infections. • Kaposi sarcoma (KS) is caused by infection with a virus
called the Kaposi sarcoma-associated herpesvirus (KSHV),
• Herpes Zoster presents with a painful, vesicular rash in a also known as human herpesvirus 8 (HHV8).
dermatomal distribution
• presents with fever, headache, and a vesicular rash. • KSHV is in the same family as Epstein-Barr virus (EBV), the
virus that causes infectious mononucleosis (mono) and is
linked to several types of cancer.
Cytomegalovirus
• a common virus.
• Once infected, your body retains the virus for life.

• Most people don't know they have cytomegalovirus (CMV)

because it rarely causes problems in healthy people.

• If you're pregnant or if your immune system is weakened, CMV

is cause for concern.
• the leading cause of congenital infections

• A newborn presents:
1. jaundice
2. hepatosplenomegaly
3. microcephaly

• Causes retinitis in patient with AIDS.

• A patient with a history of liver transplantation may develop
pneumonia.

Epstein-Barr virus
• a common and highly contagious infection.
• It spreads through bodily fluids, especially saliva (spit).
• linked to infectious mononucleosis

• presents with fever, sore throat, swollen lymph nodes and

cervical lymphadenopathy.
• Monospot test is positive.
 Miscellaneous Trigeminal Ganglion
• Also known as the semilunar or Gasserian ganglion
• A sensory ganglion located in Meckel's cave, a dural fold on
the petrous apex of the temporal bone, containing the cell
Rabies Virus bodies of the sensory neurons of the trigeminal nerve
• Presents neurological symptoms in bats, dogs, cats, and etc.
• Formation of Negri bodies in infected cells.
Congenital Infections
• Are infections transmitted from mother to child during
Negri Bodies pregnancy or delivery, potentially leading to various health
• Are characteristic, eosinophilic inclusion bodies found in the problems in the newborn, including developmental delays,
cytoplasm of nerve cells, particularly in the hippocampus and hearing loss, and birth defects
cerebellum, that are pathognomonic for rabies infection
Dermatomal Distribution
West Nile Virus • Also termed as Dermatomes
• Causes paralysis • Have a segmented distribution throughout your body.
• Vector: Mosquito
Retinitis
Rubella virus • An inflammation of the retina of the eye.
• can cause severe birth defects

Monospot Test
Hantavirus • Also known as the Heterophile Antibody Test,
• Presents hemorrhagic fever with kidney failure Mononucleosis Spot Test, Mononuclear Heterophile Test,
Heterophile Antibodies, & Mono Test
Viral Hemorrhagic Fevers
• Are infectious diseases that can be life-threatening. • A rapid screening test used to detect infectious
mononucleosis (mono) by identifying antibodies produced by
the body in response to the Epstein-Barr virus (EBV)
Rhabdoviridae
• A family of viruses that is described as having a helical
Roseola Infantum
capsid and a negative-sense RNA genome
• A common, mild, viral infection that can cause a
temperature and rash in babies and young children.
Human Papillomavirus (HPV)
• A patient develops warts on their hands Pityriasis Rosea
• The exact cause is unclear.
• It might be triggered by an infection with a virus,
Parvoviridae particularly by certain strains of the herpes virus.
• Parvovirus B19 presents a rash on their cheeks, giving a
"slapped cheek" appearance.
Infectious Mononucleosis
• Causes swollen lymph glands, fever, sore throat, and
Measles Virus extreme fatigue
• Presents a rash that starts on the face and spreads to the rest
of the body, along with fever and cough.
Infectious Diseases
• Are caused by microscopic germs (such as bacteria or
Mumps Virus viruses) that get into the body and cause problems.
• Presents a painful, swollen parotid gland

Parotid Glands
• Are major salivary glands.

Viral Pneumonia
• Causes diffuse interstitial infiltrates on chest X-ray Z

. Corticosteroid
• Along with a cool mist, it is given to a patient with a croup is
experiencing stridor at rest

Lytic Infection
• Also termed as Lytic Cycle
• A viral replication process where a virus hijacks a host cell's
machinery to rapidly replicate and then destroys the cell,
releasing new viral particles.