Epidemiologic and serologic studies of acute viral hepatitis in Brazil's Amazon Basin.

ABSTRACT

To better define the incidence and causes of acute and fulminant hepatitis, the authors studied the prevalence and incidence of hepatitis A virus (HAV) and hepatitis B virus (HBV) infection in the area of Boca do Acre, a municipality in the extreme southwest of the Brazilian Amazon. Seroprevalence studies showed both hepatitis A and hepatitis B to be highly endemic throughout this region, with most people becoming infected within the first 10 years of life. Hepatitis A caused 37% of all the observed cases, was the predominant type found among young children, and produced an epidemic disease pattern during a five-and-a-half year study period (from June 1979 to December 1984). Hepatitis B caused 48% of the cases and was a major cause of illness in both children and adults. Non-A non-B hepatitis occurred primarily in older adults. During the study period the incidences of acute and fulminant hepatitis were 3.33 and 0.365 cases per thousand inhabitants per year. Over 85 % of the fulminant hepatitis cases were found to involve active HBV infection, the patient's sera being positive for HBsAg. The single most common cause of fulminant hepatitis was delta virus superinfection of HBV carriers. The observed rates of acute and fulminant hepatitis in Boca do Acre far exceed rates previously reported in the Western Hemisphere and in other parts of Brazil. While hepatitis A and hepatitis B are both important causes of acute hepatitis, combined HBV-delta virus infection is the major cause of the unusual type of fuminant hepatitis in this region.