Factors relating to transmission of viral hepatitis in a United States military population stationed in Thailand.

To determine the incidence of clinical and inapparent hepatitis in a US military population stationed in Thailand, the authors prospectively studied a cohort of 326 men during one year. Clinical hepatitis A occurred in one man (clinical attack rate = 3.1/1000 men/year), and clinical hepatitis B was found in four men (clinical attack rate = 12.3/1000 men/year). No non-A, non-B hepatitis was identified. There was no serologically identified inapparent hepatitis A but inapparent hepatitis B occurred in 17 men. The apparent/inapparent ratio for hepatitis B was 1:4.25. Serotype analysis suggested that hepatitis B virus largely originated from Thai contacts, although 23% of cases were derived from western sources. To determine the relative contribution of 16 statistically significant (out of 67 studied) behavioral variables to the transmission of HBV, a factor analysis and a multivariate correlation analysis were employed. Factor analysis indicated that social and sexual contact with the indigenous population, including prostitutes, residence within the Thai community and marijuana use were behavioral areas that were associated with the acquisition of hepatitis B. Residence in the Thai community during the first four-month period in Thailand, sexual contact with a prostitute during the third four-month period, and ever having maintained a Thai mistress were found to be significant and independent risk factors by multiple regression analysis.