Serological evidence of the presence of groups A, B and Bunyamwera arboviruses in New York State has been reported [Bull Hyg., 1964, v. 39, 75; Am. J. Vet. Res., 1965, v. 26, 914]. In continuation of these studies a further 901 wild animal sera (amphibian, reptilian, avian and mammalian) and 192 human sera were obtained from St. Lawrence County and tested for the presence of haemagglutination inhibiting (HI) and neutralizing (NT) antibodies. Group A reactivity was tested against eastern and western encephalomyelitis viruses, group B reactivity with Powassan and St. Louis encephalitis viruses, while the Bunyamwera group was represented by Cache Valley in NT tests and by Maguari virus in HI tests.

Only a few reactions with group A viruses were found, but there was evidence of considerable activity by group B viruses-particularly Powassan virus. Of 70 sera from woodchucks (Marmota monax), 38 had both NT and HI antibodies against Powassan virus and sera from 9 other mammalian species were also reactive. Despite this high incidence in animal sera, only 2 human sera gave evidence suggesting previous infection with group B arboviruses; one had antibodies to Powassan and the other to St. Louis encephalitis virus. In the Bunyamwera group, 9 of 192 human sera neutralized Cache Valley virus, but no antibodies to this group of viruses were found in any of the 901 animal sera.