Sera collected from 60 selected South Florida patients with undiagnosed infectious disease in 1961, 1962, and 1963 were studied in hemagglutination-inhibition tests with 22 selected arboviruses. This was done in order to determine whether or not any one of the viruses caused the disease of each patient and to determine the HI antibody status of representative South Florida residents against a spectrum of arboviruses. Among the 60 patients, 11 had encephalitis, 39 had aseptic meningitis, and the illnesses of the remaining 10 were characterized as undifferentiated febrile illnesses.
Hemagglutination-inhibition antibodies were observed to 10 arboviruses in one or more of the late sera from nine patients: three were cases of encephalitis, three were aseptic meningitis and three were classified as undifferentiated febrile illnesses. The antibodies were to eight Group B viruses including bat salivary gland, Bussuquara, dengue type 2, Ilheus, Modoc, MVE, Powassan, and SLE, as well as Bunyamwera, Guaroa, Tensaw, and Tahyna. Further tests with two or more sera from those nine patients having significant levels of HI antibody revealed a significant rise in antibody titer in four patients consistent with a definitive diagnosis, at least by arbovirus grouping.
No HI antibodies were detected in sera from the 60 patients to the Group A viruses of Aura, EEE, Highland J, Una, VEE, and WEE, nor to the Group C viruses of Caraparu, Marituba, and Oriboca. Also, no HI antibodies were detected among the entire group of sera against Bussuquara, Modoc, and Powassan viruses, except for one serum which was broadly reactive to all Group B viruses used and sera from two patients having titers of 1:40 or 1:20 to two of these viruses.
Two patterns of serological reactivity were observed in cases of Group B arbovirus infection occurring in South Florida, one associated with St. Louis encephalitis and the other with dengue.