A multidisciplinary program of infectious disease surveillance along the Transamazon Highway in Brazil: Epidemiology of arbovirus infections

A program of epidemiological surveillance was conducted for two years (1974-1976) along the Transamazon Highway in Brazil's Para State. Approximately 300 randomly selected families (including about 1,600 persons) were incorporated into the study population. Visits to the study populations were conducted at six-month and two-week intervals. Blood and serum samples were collected and individual interviews were conducted during the six-monthly visits. The biweekly visits were performed to detect and document episodes of illness. The blood samples were processed for virus isolation attempts, and the sera were tested for antibodies to arboviruses. This report presents serologic data that was obtained on flaviviruses, alphaviruses, and other viruses such as Guaroa and Oropouche. It also assesses the relationship of antibody prevalences to several environmental variables. Among others results, a clearcut and consistent relationship was documented between age and sex on the one hand and acquisition of arbovirus antibodies on the other. Most arbovirus attack rates were higher for adult males than for other segments of the study population, and men who slept as well as worked in the forest were especially likely to be attacked.