The epidemiology of hepatitis A in Rio de Janeiro: environmental and domestic risk factors

A serological study of hepatitis A was carried out in low-income areas sche duled for a major sanitation programme in Rio de Janeiro, Brazil. Blood spo ts were collected by finger puncture and transported on filter paper, and t otal antibodies to hepatitis A virus were detected by ELISA. Households wer e also interviewed to collect information on their environmental conditions and socio-economic status. A generalized linear model using a complementar y log-log function was fitted to the data, using the logarithm of age as an explanatory variable to derive adjusted rate ratios (RR). The risk of infe ction was greater among households with 2-3 members per room (RR = 1.4; 95% CI = 1.04-1.8) or more than three per room (RR = 1.5; 95% CI = 1.2-2.0). P eople living on hilltops (RR = 1.5; 95% CI == 1.02-2.2), near to open sewer s (RR = 1.2; 95% CI = 1.03-1.5) or lacking a kitchen (RR = 1.4; 95% CI = 1. 08-1.9) were also at greater risk than others. The number of taps and water -using fittings in the house was associated with a protective effect (RR = 0.9 for each tap; 95% CI = 0.9-0.98). A significant protective association was found with maternal education but not with gender or household income. The results do not suggest a strong association with water quality. Ownersh ip of a ceramic water filter was associated with a protective effect on the margin of significance, but the practice of boiling drinking-water was not , nor was the type of water source used. The results suggest that that the risk of infection with hepatitis A is determined by environmental variables in the domestic and public domains.