A 4-year study of a natural tick-borne encephalitis virus focus in Hungary, 2010-2013.

A tick-borne encephalitis virus focus was identified in a former goat pasture that had been associated with a milk-borne encephalitis outbreak in 2007. Ticks and rodents were sampled monthly from April 2010 to October 2013 on two separate 0.5 ha sampling sites. At site 1, three tick-borne encephalitis virus strains were isolated from a total of 7,247 sampled ticks; 28 of the 539 tested sera (5.19%) were seropositive. At site 2, from the 2,369 sampled ticks, virus was not isolated, tests of 284 rodent sera resulted in 14 positives (4.93%). For survival, the virus needs a territory with continuously dense rodent and tick population, although observed TBEV prevalence was low both in ticks and in rodents. Sampling points of positive ticks and rodents did not coincided exactly, at a certain time only some m(2) territory is dangerous, these hot spots change unpredictably as positive ticks die or move on with their hosts.