Antibodies to arboviruses in northwestern Spain.

A survey for antibodies to arboviruses was done in the human population of the north of Spain (provinces of La Coruña, Orense, Pontevedra, Leon, Asturias). Sera were obtained from 701 persons living in the area. The hemagglutination-inhibition (HI) test showed that 16.5% of the population studied had antibodies to group B arboviruses. All sera were negative for group A and Phlebotomus fever group viruses, as well as for Tahyna and Calovo. No evidence of antibody to tick-borne encephalitis viruses was found. Neutralization tests done with several group B viruses on 56 selected sera with HI antibodies confirmed an earlier infection with West Nile and probably one other group B virus not included in the test battery. A high rate of antibody was found in young persons, indicating that epidemic activity occurred between 1961 and 1970 in the area studied.