Virology

1. •Family Picornaviridae
•Non-enveloped
•Icosahedral
Hepatitis A Virus (HAV)

2. Genome Replication
• HAV can not be propagated in the laboratory
as readily as other enteroviruses
• The virus interacts with receptors expressed
on liver cells
• Is not cytolytic and is released from liver cells
by exocytosis.
HAV : Properties of Virion

3. Resistance
HAV is resistant to
• Detergents
• Acids
• Temperature up to 60o
C
• Can survive for many months in
fresh and salt water
HAV : Properties of Virion

4. Routes of Transmission
Main Route : fecal-oral
• The virus is excreted into stool in high concentrations
• Spreads by:
° Contaminated water & food
° Dirty hands
Other Routes
• Transfusion of blood and blood products during viremia
• I.V drug abuse
HAV : Epidemiology

5. Transmission
• Most infected people are contagious before symptoms
• Outbreaks usually originate from a common source like:
° Water supply
° Restaurant
° Daycare units
• Higher incidence of HAV infection is directly related to:
° Poor hygienic conditions &
° Over-crowding.
HAV : Epidemiology

6. Seroprevalence
•Mostly children are infected
•Have mild illness
•Develop lifelong immune protection
against re-infection
HAV : Epidemiology

8. HAV : Clinical Features
Incubation period
• Between 3-5 weeks
Clinical features
• Many infections are asymptomatic
• Initial symptoms include fever, fatigue, nausea,
loss of appetite and abdominal pain
• Jaundice is common
• HAV is nearly always self limiting
• Complications such as fulminant hepatitis are rare
• Mortality : about 1/1000

10. HAV : Diagnosis
• Clinical symptoms
• The identification of a known infected source
• Immune electron microscopy for HAV feces
• HAV IgM & IgG measured by ELISA or RIA
• Clinical symptoms
• The identification of a known infected source
• Immune electron microscopy for HAV feces
• HAV IgM & IgG measured by ELISA or RIA

11. HAV : Prevention and control
• Proper hygienic measures
IMMUNIZATION
A. Passive immunization
• Immunoglobulins : Given before or shortly after exposure
• Can prevent infection in the next 3-6 months
B. Active immunization with
Hepatitis A vaccine
• There is only one serotype of HAV
• A killed HAV vaccine is available
 Routine hepatitis A vaccination for children aged 12 to 23
months and for adults who are at high risk for infection.

12. Hepatitis E Virus (HEV)
Taxonomy and structure
• Belongs to family Caliciviridae.
Epidemiology and control
• World-wide distribution
• Predominantly spreads by fecal-oral route
• Especially through contaminated water

15. HEV : Pathogenesis &
Clinical Syndromes
• Are similar to that of HAV
• Causes only acute disease
• Incubation period is longer
• HEV infection is specially serious in
pregnant women with a mortality rate of 20%

16. Hepatitis G Virus (HGV)
• Resembles HCV in many aspects
• Belongs to the family Flaviviridae
• Probably has a predilection for chronic disease
• So far, HGV infection can only be diagnosed
by detection of genome by PCR.