An outbreak of Oropouche virus disease in the vicinity of Santarem, Para, Brazil

An epidemic of human febrile illness caused by Oropouche virus was studied in the village of Mojui dos Campos, Para State, in February 1975. The major clinical symptoms, fever, chills, headache, myalgia, arthralgia and dizziness persisted for 2 to 7 days. Leukopenia was commonly observed. Some patients were severely ill but no deaths were attributed to the disease. Recurrence of symptoms was reported in several people. 55 Cases of recent infection were diagnosed in Mojui dos Campos between February and April. In the same period 26 cases were recorded from the Palhal area, near Mojui. Two additional cases were observed, 12 and 20 km from Mojui, respectively. Of the 83 infections, 65 were proven by virus isolation from blood of patients and 18 by the demonstration of an increasing antibody level to the agent. Both sexes of the population were infected in equal proportions. Most patients were below 20 yr of age. In the village of Mojui dos Campos with a population of about 2,900, 45 (40.1%) out of 112 students aged 4 to 18, had HI antibodies to the virus when examined late in February. The epidemic, however, only declined after the middle of March. Two isolations of Oropouche virus were obtained from some 15,000 Culicoides inoculated into mice. About 4,000 Culicoides and all the 9,420 mosquitoes captured during the outbreak remain to be inoculated. Over 95% of the Culicoides were C. paraensis. Only 1 rodent of the genus Proechimys had HI antibodies to Oropouche virus out of the 602 wild and domestic mammals captured in the area. All 5 reptiles examined were negative. 34 (4.9%) out of the 681 wild birds and 12 (5.8%) out of the 206 domestic birds examined were positive for the presence of HI antibodies to the agent.