Human infection with tick-borne encephalitis virus in the Tribec region.

The isolation of tick-borne encephalitis (TBE) virus from the spinal fluid of a patient with a clinical diagnosis of meningo-encephalitis and the demonstration of virus-neutralizing antibodies in sera from inhabitants of the Tribec region have shown this area to be an active natural focus of tick-borne encephalitis. Of healthy people from the villages of Jarok and Kostolany, 26% had antibodies to TBE virus. Children from Kostolany had no such antibodies, whereas in Jarok 7% of children less than 15 years old were serologically positive. This finding, together with the generally higher antibody titres of sera from inhabitants of Jarok, suggests that this elementary focus of tick-borne encephalitis has been active more recently than that in Kostolany. In both villages the frequency of antibodies was high in persons over 55 years old (50% in Jarok and 63% in Kostolany); the highest frequency was found in those working regularly within the natural focus, i.e., forest workers and housewives.