Hepatitis B virus infection in immigrants to the southern Brazilian Amazon

To identify epidemiological patterns and risk factors associated with hepatitis B virus (HBV) infection in the southern Brazilian Amazon, a survey was performed in the county of Terra Nova do Norte in the northern part of the state of Mato Grosso. The population consists mainly of immigrants from the southern part of Brazil, where HBV prevalence is low. A random sample (n = 783) of the population was interviewed and tested for HBV markers. The overall prevalence of HBV infection was 54.7%. There were 31 hepatitis B surface antigen (HBsAg) carriers (3.9%), with a low rate of HBV e antigen positivity, and none with anti-hepatitis D virus. Subtypes ayw3 and ayw2 of HBsAg were predominant, suggesting that the immigrants carried HBV from their original region to the Amazon. Clustering of HBV infection within families was found. The association between HBV markers and having lived in a gold-miners' camp, even after adjusting for confounders, indicated that the gold-miners may play a role in HBV spread in areas of the Amazon where gold prospecting occurs.