First report outside Eastern Europe of West Nile virus lineage 2 related to the Volgograd 2007 strain, northeastern Italy, 2014.
BACKGROUND
West Nile virus (WNV) is a Flavivirus transmitted to vertebrate hosts by mosquitoes, maintained in nature through an enzootic bird-mosquito cycle. In Europe the virus became of major public health and veterinary concern in the 1990s. In Italy, WNV re-emerged in 2008, ten years after the previous outbreak and is currently endemic in many areas of the country. In particular, the northeastern part of Italy experience continuous viral circulation, with human outbreaks caused by different genovariants of WNV lineage 1, Western-European and Mediterranean subcluster, and WNV lineage 2, Hungarian clade. Alongside the WNV National Surveillance Program that has been in place since 2002, regional surveillance plans were implemented after 2008 targeting mosquitoes, animals and humans.


RESULTS
In July and September 2014, West Nile virus lineage 2 was detected in pools of Culex pipiens s.l. mosquitoes from northeastern Italy. Whole genome sequencing and phylogenetic analysis of two representative samples identified the presence of WNV lineage 2 related to the Volgograd 2007 strain (99.3 % nucleotide sequence identity), in addition to WNV lineage 2 Hungarian clade.


CONCLUSIONS
This is the first evidence of the circulation of a WNV lineage 2 strain closely related to the Volgograd 2007 outside Eastern Europe, where it has caused large human outbreaks. This strain may pose a new threat to animal and human health in Italy.
Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy. sravagnan@izsvenezie.it.
Silvia
S
Ravagnan
Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy. fmontarsi@izsvenezie.it.
Fabrizio
F
Montarsi
Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy. scazzin@izsvenezie.it.
Stefania
S
Cazzin
Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy. eporcellato@izsvenezie.it.
Elena
E
Porcellato
Promotion and Development of Hygiene and Public Health, Veneto Region, Venezia, Italy. francesca.russo@regione.veneto.it.
Francesca
F
Russo
Veterinary Public Health Service, Friuli Venezia Giulia Region, Udine, Italy. manlio.palei@regione.fvg.it.
Manlio
M
Palei
Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy. imonne@izsvenezie.it.
Isabella
I
Monne
Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise, Teramo, Italy. g.savini@izs.it.
Giovanni
G
Savini
Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy. smarangon@izsvenezie.it.
Stefano
S
Marangon
Department of Molecular Medicine, University of Padova, Padova, Italy. luisa.barzon@unipd.it.
Luisa
L
Barzon
Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, Padova, Italy. gcapelli@izsvenezie.it.
Gioia
G
Capelli
D000818:Animals; D003465:Culex / Q000821:virology*; D007558:Italy; D010802:Phylogeny; D014902:West Nile virus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*