Viral hepatitis comparative epidemiology.

The epidemiology of HAV, HBV, HCV, HDV and HEV is compared. Spread of HAV and HEV is by the faecal/oral route whereas HBV, HCV and HDV are spread by blood or blood products. HEV is more likely to produce large epidemics than HAV but sporadic cases also occur. HBV, HCV and HDV all occur after blood transfusion, in haemophiliacs and intravenous drug abusers but they differ in their geographical distribution and in the frequency of perinatal transmission which is only common with HBV. Superinfection and interaction between these viruses is discussed.