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Lecture 8a - HAV-HEV-HGV-RMC

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Virology

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Lecture 8a - HAV-HEV-HGV-RMC

  1. 1. •Family Picornaviridae •Non-enveloped •Icosahedral Hepatitis A Virus (HAV)
  2. 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. 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. 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. 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. 6. Seroprevalence •Mostly children are infected •Have mild illness •Develop lifelong immune protection against re-infection HAV : Epidemiology
  7. 7. 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
  8. 8. 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
  9. 9. 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.
  10. 10. 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
  11. 11. 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%
  12. 12. 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.

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