Fig 1. Photos illustrating typical life in the surveyed region.

(A) Typical palaffitte houses of the river-dweller communities in the Amazonas region (ribeirinhos). These wooden houses are built over the land and float when water covers the area. (B) Ribeirinhos have easy access to fish, fluvial transportation and other activities. (C) Usual way to carry out the surveys in the riverside-dweller communities. The researcher (ASM-G) is examining the medication showed by the ribeirinho woman. (D) Small market in one of the riverside-dweller communities included in the study. Medicines aretypically sold in those shops.