The aim of this study was to reconstruct the origin and dispersion of WNV-2 in Central Europe and Italy on a phylodynamic and phylogeographical basis

The aim of this study was to reconstruct the origin and dispersion of WNV-2 in Central Europe and Italy on a phylodynamic and phylogeographical basis. the corners or sides respectively represent tree-like (fully resolved phylogenies in which one tree is clearly better than the others) or network-like phylogenetic signals (three regions in which it is not possible to decide between two topologies). The central area of the map represents a star-like signal (the region in which the star tree is the optimal tree). The numbers indicate the percentage of dots in the centre of the triangle.(TIF) pone.0179679.s004.tif (22K) GUID:?778BEFE6-6260-4624-82AF-ADEA7364FF45 S1 Video: Animated visualization of the continuous pattern of WNV-2 dispersion in Italy in the years 2008C2015. (MP4) pone.0179679.s005.mp4 (238K) GUID:?D245F7FC-89F5-4CB7-829E-9200A4759F8A Data Availability StatementAll relevant data are within the paper, its Supporting Information files, and available within the NCBI at the accession numbers listed in S1 Table. Abstract West Nile virus lineage 2 (WNV-2) was mainly confined to sub-Saharan Africa until the early 2000s, when it was identified for the first time in Central Europe causing outbreaks of human and animal infection. The aim of this study was to reconstruct the origin and dispersion of WNV-2 in Central Europe and Italy on a phylodynamic and phylogeographical basis. To this aim, discrete and continuous space phylogeographical models were applied to a total of 33 newly characterised full-length viral genomes obtained from mosquitoes, birds and humans in Northern Italy in the years 2013C2015 aligned with 64 complete sequences isolated mainly in Europe. The European isolates segregated into two highly significant clades: a small one including three sequences and a large clade including the majority of isolates obtained in Central Europe since 2004. Discrete phylogeographical analysis showed that the most probable location of the root of the largest European clade was in Hungary a mean 12.78 years ago. The European clade bifurcated into two highly supported subclades: one including most of the Central/East European isolates and the other encompassing all of the isolates obtained in Greece. The continuous space phylogeographical analysis of the Italian clade showed that WNV-2 MDL 28170 entered Italy in about 2008, probably by crossing the Adriatic sea and reaching a central area of the Po Valley. The epidemic then spread simultaneously eastward, to reach the region of the Po delta in 2013, and westward to the border area between Lombardy and Piedmont in 2014; later, the western strain changed direction southward, and reached the central area of the Po valley once again in 2015. Over MDL 28170 a period of about seven years, the virus spread all over an area of northern Italy by following the Po river and its main tributaries. Introduction West Nile virus (WNV) is a neurotropic mosquito-borne virus belonging to the Flavivirus genus and Japanese encephalitis virus serogroup [1]. Its genome is represented by Gja8 a single-stranded positive-sense RNA molecule coding for a single polyprotein encompassing a total of three structural proteins corresponding to the viral core, membrane and envelope, and seven non-structural proteins. WNV is maintained by an enzootic cycle involving birds (particularly birds of the order and migratory birds) and ornithophilic mosquitoes such as species of the genus. Humans, horses and other mammals are dead-end hosts MDL 28170 that may be incidentally involved in the enzootic cycle. Most human infections are asymptomatic, whereas fever may occur in 20% of cases and neuroinvasive disease in less than 1% [1]. WNV was first isolated in a febrile woman in Uganda in 1937 [2], and sporadic cases and small outbreaks were documented in Africa, the Middle East and Europe during the 1950s-1960s [3]. In 1996, a major outbreak in Romania was characterized by a high (10%) fatality rate and more MDL 28170 than 350 people with neurological symptoms [4]; since then, there have been a number of equine or human outbreaks in various parts of the Mediterranean area and central Europe [5, 6]. In 1999, the virus was introduced into New York City, where it caused a dramatic outbreak that spread throughout the entire Western hemisphere in subsequent years {CDC, 1999 #41; [7]. Phylogenetic studies of WNV have revealed MDL 28170 the existence of at least eight evolutionary lineages, of which lineages 1 and 2 represent the most important human pathogens [6]. Lineage 1 is widespread in all continents, whereas lineage 2 was mainly confined to sub-Saharan Africa until the early 2000s, when the virus emerged in eastern Europe: two different strains of lineage 2 were respectively detected for the first time in Hungary and southern Russia in 2004, and led to outbreaks among wild birds with some cases of human infection [8, 9]. The first human cases of infection due to WNV-2 in Europe were reported in Hungary in 2008 [10]. In the following years, WNV-2 has been regularly identified every year as the cause of local outbreaks or sporadic cases of.