S-45. Epidemiology of hepatitis viruses

The term ‘hepatitis viruses’ encompasses several hepatotropic viruses with varying morphology, genomic organization, biological properties and routes of spread, which cause inflammation of the liver that presents clinically as acute onset of jaundice preceded frequently by a short prodromal illness. Currently, 5 such viruses are known.

Hepatitis A and hepatitis E are transmitted by fecal-oral route, and usually cause self-limited illness lasting a few weeks, though some patients develop fulminant disease with a high mortality rate. Hepatitis A shows varying epidemiological patterns based on level of socio-economic development and age at the time of infection. It is associated with frequent person-to-person transmission, higher rate of clinical disease with increasing age and life-long immunity against re-infection. Hepatitis E is characterized by high attack rate among young adults, a low rate of intra-familial spread, and particularly severe illness and high mortality rate among pregnant women. Lasting immunity appears unlikely. Hepatitis B and C are transmitted parenterally, i.e. through transfusion of blood and blood products, unsafe injection practices, and through contact with infected body secretions. Both infections, in particular hepatitis B, can also be transmitted from pregnant mother to their newborns. Both infections can become persistent, lasting for years and even life-long. Chronic infection is associated with increased risk of liver cirrhosis and liver cancer. In hepatitis B, the risk of chronicity depends on age at the time of infection. Hepatitis D virus, which depends on hepatitis B virus for its multiplication, shares several epidemiological features of the latter infection.