[Role of Powassan virus in the etiological structure of tick-borne encephalitis in the Primorsky Kray].

Composite studies conducted annually in the Primorsky kray showed the tick-borne encephalitis virus to play the main etiological role in the group of encephalites with the spring-summer incidence. In 1976--1978, virological studies of 69 cases of the disease yielded 11 strains of tick-borne encephalitis virus. In 1978, from the blood of clinically normal woman after a tick bite strain 555 was first isolated which was identified as Powassan virus, and antigenemia was observed for 53 days using the fluorescent antibody technique. In the same period, serological examinations of the blood sera from 117 patients demonstrated antibody to tick-borne encephalitis virus in 69.2%, to Powassan virus in 4,3% and to both viruses simultaneously in 4.3%. Besides, antibody to tick-borne encephalitis virus, Powassan virus and both viruses simultaneously was found in patients with progredient forms of tick-borne encephalitis and in subjects with the history of tick attachment.