OUTBREAK OF HEPATITIS-B VIRUS IN RECENT ARRIVALS TO THE BRAZILIAN AMAZON

An outbreak of acute hepatitis cases in a small community took place 6 months after the community's arrival to the Brazilian Amazon. An epid emiological investigation was performed and included residents aged mo re than two years. Study subjects were interviewed and bled to test fo r hepatitis markers by enzyme immunoassays. Around 80% of the village population was surveyed. The overall prevalence of hepatitis B virus ( HBV) markers was 75.1% (281/374). The surface antigen of HBV (HBsAg) a nd the IgM class antibody against hepatitis B core antigen (IgM anti-H Bc) were present in 10.4% and 9.6%, respectively. Evidence of HBV-HDV (Delta virus) coinfection or hepatitis C infection was not found. IgM class antibody against hepatitis A virus was uncommon (3.7%). Follow-u p evaluation 6 and 12 months later were carried out to identify new HB V infections. An incidence rate of 7.2 new infections per 100 exposed subjects per month was found. Average individual risk for HBV infectio n among susceptible inhabitants of the village between June 1995 and J une 1996 can be estimated at 57.6%. The predominant HBsAg subtype foun d (ayw3) suggests that immigrants may have carried HBV from the origin al area. Time living in the study region was significantly associated with HBV markers in analysis for linear trend and logistic regression analysis. Environmentally related factors may have facilitated HBV tra nsmission. J. Med. Virol. 56:4-9, 1998. (C) 1998 Wiley-Liss, Inc.