West nile virus infection: re-emergent disease in Croatia]

West Nile virus (WNV) is a small, enveloped, spherical virus that belongs to the family Flaviviridae, genus Flavivirus, Japanese encephalitis serocomplex. Natural reservoirs of WNV are birds, and the main vectors are mosquitoes of the genus Culex. There are seven genetic lineages of WNV. Lineages 1 and 2 are the most widely distributed (Africa, North and South America, Europe, Asia and Australia). About 80% of infections are asymptomatic. In 20% of patients nonspecific febrile disease occurs (West Nile fever). Less than 1% of infected persons will develop neuroinvasive WNV disease (meningitis, encephalitis, and poliomyelitis). In Croatia, antibodies to WNV were demonstrated in humans,bears and horses. In August-September 2012 clinical cases of human WNV neuroinvasive disease and asymptomatic acute infection in horses were reported for the first time in three eastern Croatian counties. The diagnosis was confirmed by serologic tests (enzyme immunoassay, IgG avidity, plaque-reduction neutralization test).