Horizontal transmission of hepatitis B virus.

Meta-analysis of seroprevalence surveys shows that horizontal transmission of hepatitis B virus (ie, that occurring without apparent parenteral, sexual, or perinatal exposure) is common in areas endemic for the virus. It occurs especially in pre-adolescent children. In developed countries, where endemicity of hepatitis B virus is low, horizontal transmission (probably via saliva or open wounds) may occur in households with a persistent carrier, but it is less efficient a means of infection than is sexual or perinatal transmission. Horizontal transmission also seems possible in pre-school day-care centres in developed countries, despite the small numbers of carriers in such places.