A nationwide seroprevalence screening for West Nile virus and Tick-borne encephalitis virus in the population of Bulgaria.

To assess local circulation and risk for human infections with West Nile virus (WNV) and Tick-borne encephalitis virus (TBEV) in Bulgaria, a nationwide seroprevalence study was conducted. In total, 1451 residents of all 28 districts in Bulgaria were tested for WNV-specific and TBEV-specific IgG antibodies. The survey found overall seroprevalence of 1.5% and 0.6%, respectively. The highest WNV seroprevalence was found in Sofia Province and districts near the river Danube. TBEV circulation was detected among residents of six districts. The results showed that the two virus infections seem to be more wide-spread in the country as has been described.