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 epidemiological investigation was performed and included residents aged more than two years. Study subjects were interviewed and bled to test for 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) and the IgM class antibody against hepatitis B core antigen (IgM anti-HBc) 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-up evaluation 6 and 12 months later were carried out to identify new HBV infections. An incidence rate of 7.2 new infections per 100 exposed subjects per month was found. Average individual risk for HBV infection among susceptible inhabitants of the village between June 1995 and June 1996 can be estimated at 57.6%. The predominant HB-sAg subtype found (ayw3) suggests that immigrants may have carried HBV from the original 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 transmission.

Hepatitis B virus infection in hemodialysis units: clinical features, epidemiological markers and general control measures.

1. A total of 140 patients and 41 staff members were submitted to periodic testing for HBsAg from January 1979 to December 1984 at the Hemodialysis Unit of the University Hospital, Faculty of Medicine of Ribeirão Preto, University of São Paulo. Twenty-two HBsAg-positive subjects were detected during this period, 15 of whom had acquired the hepatitis B virus (HBV) in the Unit (10 patients and 5 staff-members). 2. HBV prevalence was not uniform throughout the period of study, with an increase of hepatitis B cases occurring after September 1981 and reaching epidemic proportions which lasted until January 1983. 3. Among the preventive measures adopted, epidemiological alert, grouping patients and workers according to susceptibility or immunity to the infection, and setting up a separate area for the dialysis of infected patients appeared to be most important. 4. The use of HBV subtyping as an epidemiological marker permitted us to demonstrate that HBV was introduced into the Unit by chronic carrier patients and spread internally through the probable contamination of equipment and unit environment.