Mosquito-borne viruses in Finland.

Inkoo virus, the Finnish representative of the California group, was isolated from a pool of Aedes communis/punctor. It is distinguishable from Tahyna, California encephalitis, Trivittatus and Melao viruses, but seems to be antigenically related to the Jamestown Canyon virus. The prevalence of Inkoo antibodies increases towards the north in both human beings (16% to 69%) and cows (37% to 88%). Inkoo antibodies are common also in other mammals of large size (reindeer, moose, foxes), less frequent in snow hares, rare in hazel grouse and not detected in other birds and small mammals. Some show hare serum samples react with Inkoo virus only in the hemmaglutination inhibition test suggesting the existence of another California group virus in Finland. In addition, antibodies against some other mosquito-borne viruses have been found in Finland. A Batai virus epizootic among cows may have occured in the early 1960's in southern coastal Finland, and some serological data point to the existence of alphaviruses in Finland. The overwintering mechanism of the Finnish mosquito-borne viruses is still unsolved.