A serological survey for hemagglutination-inhibition antibodies to 17 arbovirus was carried out in households with cases of Rocio encephalitis, in the urban zone of four cities of the Ribeira Valley, Brazil, where an epidemic of Rocio encephalitis occurred recently. Among those households the prevalence of Rocio antibodies was not higher than in households without cases of encephalitis. Some facts, which were reported before, were again observed: a large prevalence of antibodies in men, particulary fishermen, an increase of antibodies with age and the presence of one past case of encephalitis that presented only neutralizing antibodies against EEE. That Alphavirus has never been responsible for human disease in the area. There is also a very small proportion of people with Rocio and Flavivirus antibodies which, in view of the recent epidemic, was surprising.
Arboviruses; Serological surveys; Encephalitis; Flavivirus Rocio