West Nile virus lineage 2 in free-living Corvus cornix birds in Poland

Abstract

The summer temperatures recorded in Poland in 2022 were among the highest in over30 years and, combined with higher-than-expected rainfall, gave the impression of an almost tropicalclimate. Such climatic conditions were ideal for the transmission of vector-borne zoonotic diseasessuch as West Nile fever. In northeastern Poland, in the Mazowieckie region, the Polish event-basedsurveillance network reported increased fatalities of free-living hooded crows (Corvus corone cornix).West Nile virus (WNV) lineage 2 was identified for the first time as the etiological agent responsiblefor the death of the birds. WNV was detected in 17 out of the 99 (17.17%) free-living birds tested inthis study. All the WNV-infected dead birds were collected in the same area and were diagnosed inSeptember by the NVRI and confirmed by the EURL for equine diseases, ANSES, in October 2022.Unnaturally high temperatures recorded in Poland in 2022 likely favored the infection and spread ofthe virus in the avian population. A nationwide alert and awareness raising of blood transfusioncenters and hospitals was carried out to prevent human infections by WNV.