INFLUENCE OF MIGRATION ON PREVALENCE OF S EROLOGICAL HEPATITIS-B MARKERS IN A RURAL-COMMUNITY .1. ANALYSIS OF PREVALENCE BY BIRTHPLACE

Distribution of hepatitis B serological markers according to people's birthplaces and area of residence (urban/rural) was studied as a part of a field epidemiological research project carried out in Cassia dos Coqueiros, a small rural community of S. Paulo State, Brazil. The tota l prevalence of HBV markers was 7.7%, with rural showing a higher risk than urban inhabitants (9.8% as against 4.9%, respectively). Analysis of prevalence according to people's birthplaces revealed the highest value among those from other Brazilian states (15.8%), followed by peo ple from other municipalities of the State of S. Paulo (9.2%). Those b orn in Cassia dos Coqueiros and particularly in Ribeirao Preto (the ma in city of the area, located 80 kilometers away), showed the lowest va lues of prevalence (5.2% and 2.5%, respectively). The importance of st udying people's birthplaces when field epidemiological studies on hepa titis B are carried out is stressed. This variable is considered to be capable of exercising an influence on the natural history of the dise ase in a community, and may even explain differences in the distributi on of markers in apparently similar populations.