[Seroprevalence of American trypanosomiasis in adults in an area of the western Brazilian Amazon region].

From January to March 2001 a seroepidemiological survey for American trypanosomiasis (Chagas disease) was carried out among urban and rural human populations in areas of the Upper Purus basin, in the western Brazilian Amazon region, using serial testing with three different serological techniques. The sample was composed of 1,055 individuals: 844 from urban and 211 from rural areas. Autochthonous infection was identified in nine individuals aged 16 to 72 years: five from urban and four from rural areas. The estimated prevalences of Chagas infection for the urban and rural areas were 0.6% (95% CI: 0.2-1.4) and 1.9% (95% CI: 0.6-4.5) respectively. An apparent clustering trend was noted: seven were born along the Purus river: three lived at the same locality and two of them in the same dwelling.