Heterosexual transmission as the most common route of acute hepatitis B virus infection among adults in Taiwan--the importance of extending vaccination to susceptible adults.

Sixty adult patients with acute viral hepatitis B (AVHB) and 93 controls were interviewed to assess potential risk factors of hepatitis B. Heterosexual contact was the only significant factor, and it was associated with 83% of cases. A history of having new sex partners or multiple sex partners within 6 months before the onset of AVHB or first sexual contact before 20 years of age were significantly associated with HBV infection (P < .005, respectively). There was a dose-response relationship between the number of sex partners and the risk of HBV infection. In multivariate analyses, a history of having new sex partners was the most important factor. Moreover, 18 of 24 sex partners of the patients were serum hepatitis B surface antigen- and HBV DNA-positive. Heterosexual contact is, therefore, the predominant route of HBV transmission among adults in Taiwan. Susceptible adults should receive vaccination.