Early start of seasonal transmission and co-circulation of West Nile virus lineage 2 and a newly introduced lineage 1 strain, northern Italy, June 2022 br

In spring 2022, Europe faced an unprecedented heat -wave, increasing the risk of West Nile virus (WNV) out-breaks. As early as 7 June 2022, WNV was detected in Culex mosquitoes in northern Italy, and -in the following days -in two blood donors, a patient with encephalitis, wild birds and additional mosquito pools. Genome sequencing demonstrated co-circulation of WNV lineage 2 and a newly introduced WNV lineage 1, which was discovered in the region in 2021.