Yale Arbovirus Research Unit, Department of Epidemiology and Public Health, Yale University School of Medicine, 60 College Street, U.S. Army Medical Research Institute of Infectious Diseases, Box 3333, New Haven, Connecticut 06510
The antigenic relationship of the 31 currently recognized phlebotomus fever group viruses was examined by plaque reduction neutralization test. Although some low-level cross-neutralization was observed, each of the viruses was easily differentiated by this method. Rift Valley fever virus was shown to be antigenically related to Candiru, Frijoles, Karimabad and Punta Toro viruses. Naples, Tehran and Toscana viruses were also shown to be closely related. Preliminary results of indirect fluorescent antibody tests indicate that this technique is broadly reacting and less specific than either the complement-fixation or neutralization test for identifying phlebotomus fever group viruses. A discussion follows on some of the difficulties encountered in attempting to classify phleboviruses.