Indication of West Nile Virus (WNV) Lineage 2 Overwintering among Wild Birds in the Regions of Peloponnese and Western Greece

SIMPLE SUMMARY: West Nile virus (WNV) is one of the most widespread zoonotic arboviruses worldwide and wild avian species act as its amplifying hosts in nature. In the present study, WNV circulation among wild birds was evaluated in two regions of Greece during 2022. A total of 511 birds were sampled and screened for WNV RNA. The virus was detected in 71 samples from both regions, during February to November. Population density and distance from water sources were identified as important factors associated with WNV occurrence. In conclusion, these findings show that WNV circulated in both investigated regions of Greece during 2022, highlighting the need for avian species surveillance to be conducted annually and throughout the year. Magpies are proposed as sentinels for WNV monitoring. ABSTRACT: West Nile virus (WNV), a zoonotic mosquito-borne virus, has recently caused human outbreaks in Europe, including Greece. Its transmission cycle in nature includes wild birds as amplifying hosts and ornithophilic mosquito vectors. The aim of this study was to assess WNV circulation among wild birds from two regions of Greece, Peloponnese and Western Greece, during 2022. To this end, a total of 511 birds belonging to 37 different species were sampled and molecularly screened. WNV RNA was detected from February to November in a total of 71 wild birds of nine species originating from both investigated regions. The first eight positive samples were sequenced on a part of NS3 and, according to the phylogenetic analysis, they belonged to evolutionary lineage 2 and presented similarity to previous outbreak-causing Greek strains (Argolis 2017, Macedonia 2010 and 2012). It was more likely to identify a PCR positive bird as the population density and the distance from water sources decreased. The present report provides evidence of WNV occurrence in both Peloponnese and Western Greece during 2022 and underlines its possible overwintering, highlighting the need for avian species surveillance to be conducted annually and throughout the year. Magpies are proposed as sentinels for WNV monitoring.