•Family Picornaviridae•Non-enveloped •Icosahedral

Hepatitis A Virus (HAV)

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

Resistance HAV is resistant to • Detergents • Acids • Temperature up to 60oC• Can survive for many months in

fresh and salt water

HAV : Properties of Virion

Routes of TransmissionMain 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

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

Seroprevalence •Mostly children are infected •Have mild illness •Develop lifelong immune protection against re-infection

HAV : Epidemiology

HAV : Clinical FeaturesIncubation 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

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

HAV : Prevention and control• Proper hygienic measuresIMMUNIZATION A. Passive immunization• Immunoglobulins : Given before or shortly after exposure • Can prevent infection in the next 3-6 months

B. Active immunization withHepatitis 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.

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

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%

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.