Hepatitis B in Australia: determinants of intrafamily spread.

Strategies for the control of hepatitis B virus (HBV) infection rely on information about the modes of spread and the numbers of 'at risk' individuals in particular community subgroups. This study prospectively examined 377 family and household contacts of 145 patients with HBV infection to determine the incidence of and factors determining intrafamily spread. Two hundred and forty were contacts of 68 Asian patients and 137 were contacts of 77 Caucasian patients. Serological examination of all contacts demonstrated that 161 (43%) had HBV markers including 60 (16%) who were HBsAg positive. HBV transmission within families was greater if the index case was Asian rather than Caucasian (p less than 0.001), had an HBsAg positive mother rather than an HBsAg positive father (p less than 0.01), was HBeAg positive rather than HBeAg negative (p less than 0.002), and had chronic rather than acute HBV infection (p less than 0.001). However birthplace, family size, and the activity of the liver disease of the index case did not influence HBV transmission. Within Asian families, the risk of non-sexual and non-vertical transmission of hepatitis B appeared to be as high as 18% and continued after the first three years of life. It is concluded that hepatitis B prevention programmes should include vaccination of families of chronic HBV carriers, particularly those from endemic regions such as Asia.