PRIMEIRO REGISTRO DE EPIDEMIAS CAUSADAS PELO VIRUS OROPOUCHE NO ESTADO DO AMAZONAS

A description of the first outbreaks of Oropouche fever recognized in Amazonas State is presented. One outbreak occurred in the town of Barcelos from May to July 1980, and a second in Manaus from October 1980 to February 1981. In addition to the classical clinical manifestations of the illness, several patients exhibited clinical signs of meningitis, and in others a skin rash was noted. Nine strains of Oropouche virus were obtained from the blood of sick persons. A hemagglutination inhibition antibody prevalence rate of 4.2% (range of 0 to 12.0%) was found in 496 randomly selected residents of six districts of Manaus who were bled at the beginning of the epidemic; 1.8% of these persons had low antibody titers, probably resulting from past infections. This indicates a low level of Oropouche virus endemicity in Manaus prior to the outbreak. An antibody prevalence rate of 16.7% (range of 0 to 40.6%) was found in the same population at the end of the epidemic, suggesting that 5,000 of the 35,000 inhabitants of those districts acquired the infection during the outbreak. Assuming that the sample of 496 persons is representative of the entire population of Manaus, it may be concluded that there were approximately 97,000 infections among the 650,000 inhabitants of Manaus. In Barcelos, 64.7% (171/264) of suspected cases of Oropouche disease examined during convalescence had immunity to the agent. Mouse inoculation of 5,848 Culicoides paraensis and 1,034 Culex p. quinquefasciatus collected in Manaus resulted in one single isolation of Oropouche virus, from the biting midges.