West Nile Virus Lineage 1 in Italy: Newly Introduced or a Re-Occurrence of a Previously Circulating Strain?

In Italy, West Nile virus (WNV) appeared for the first time in the Tuscany region in 1998. After 10 years of absence, it re-appeared in the areas surrounding the Po River delta, affecting eight provinces in three regions. Thereafter, WNV epidemics caused by genetically divergent isolates have been documented every year in the country. Since 2018, only WNV Lineage 2 has been reported in the Italian territory. In October 2020, WNV Lineage 1 (WNV-L1) re-emerged in Italy, in the Campania region. This is the first occurrence of WNV-L1 detection in the Italian territory since 2017. WNV was detected in the internal organs of a goshawk (Accipiter gentilis) and a kestrel (Falco tinnunculus). The RNA extracted in the goshawk tissue samples was sequenced, and a Bayesian phylogenetic analysis was performed by a maximum-likelihood tree. Genome analysis, conducted on the goshawk WNV complete genome sequence, indicates that the strain belongs to the WNV-L1 Western-Mediterranean (WMed) cluster. Moreover, a close phylogenetic similarity is observed between the goshawk strain, the 2008–2011 group of Italian sequences, and European strains belonging to the Wmed cluster. Our results evidence the possibility of both a new re-introduction or unnoticed silent circulation in Italy, and the strong importance of keeping the WNV surveillance system in the Italian territory active.

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Phylogenetic analysis of West Nile virus isolated in Italy in 2008

Eurosurveillance ◽

10.2807/ese.13.48.19048-en ◽

2008 ◽

Vol 13 (48) ◽

Author(s):

G Savini ◽

F Monaco ◽

P Calistri ◽

R Lelli

Keyword(s):

Phylogenetic Analysis ◽

West Nile Virus ◽

Late Summer ◽

Columba Livia ◽

River Delta ◽

Pica Pica ◽

West Nile ◽

Po River ◽

E Protein ◽

First Occurrence

In Italy the first occurrence of West Nile virus (WNV) infection was reported in Tuscany region during the late summer of 1998. In August 2008, the WNV infection re-emerged in Italy, in areas surrounding the Po river delta, and involving three regions Lombardy, Emilia Romagna and Veneto. WNV was isolated from blood and organs samples of one horse, one donkey, one pigeon (Columba livia) and three magpies (Pica pica). The phylogenetic analysis of the isolates, conducted on 255 bp in the region coding for the E protein, indicates that these isolates belong to the lineage I among the European strains. According to the analysis, both the 1998 and 2008 Italian strains as well as isolates from Romania, Russia, Senegal and Kenya fell in the same sub-cluster.

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Genetic Characterization of a Neurovirulent West Nile Virus Variant Associated with a Fatal Great Grey Owl Infection

Viruses ◽

10.3390/v13040699 ◽

2021 ◽

Vol 13 (4) ◽

pp. 699

Author(s):

Katarína Peňazziová ◽

Ľuboš Korytár ◽

Patrik Pastorek ◽

Juraj Pistl ◽

Diana Rusňáková ◽

...

Keyword(s):

West Nile Virus ◽

Genetic Characterization ◽

Fatal Case ◽

The Novel ◽

West Nile ◽

Tissue Samples ◽

Principal Vector ◽

Virus Variant ◽

Lineage 2

This study reports on a fatal case of a captive great grey owl infected with the West Nile virus (WNV) in the zoological garden Košice, eastern Slovakia (Central Europe). The tissue samples of the dead owl were used for virus isolation and genetic characterization. The novel isolate is genetically closer to Hungarian, Greek, and Bulgarian strains from the central/southern European clade of lineage 2 than to the strains previously isolated in Slovakia. Interestingly, it carries NS3-249P, a molecular virulence determinant associated with higher neurovirulence, which has not previously been observed in Slovakia. Subsequent serological investigation of the captive owls revealed additional seropositive animals, indicating local WNV transmission. Although no WNV-positive mosquitoes were found, the presence of the WNV principal vector Culex pipiens complex together with the described fatal case and further serological findings indicate an endemic focus of bird-neurovirulent WNV variant in the area.

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Faculty Opinions recommendation of Equine encephalomyelitis outbreak caused by a genetic lineage 2 West Nile virus in Hungary.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.10115956.10883054 ◽

2011 ◽

Author(s):

Lyle Petersen

Keyword(s):

West Nile Virus ◽

Genetic Lineage ◽

West Nile ◽

Lineage 2

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Epidemiology of West Nile Virus Infections in Humans, Italy, 2012–2020: A Summary of Available Evidences

Tropical Medicine and Infectious Disease ◽

10.3390/tropicalmed6020061 ◽

2021 ◽

Vol 6 (2) ◽

pp. 61

Author(s):

Matteo Riccò ◽

Simona Peruzzi ◽

Federica Balzarini

Keyword(s):

West Nile Virus ◽

Age Groups ◽

Invasive Disease ◽

Incidence Rates ◽

Annual Incidence ◽

Virus Infections ◽

West Nile ◽

Po River ◽

Air Temperatures ◽

Sex Risk

In Italy, human cases of West Nile virus (WNV) infection have been recorded since 2008, and seasonal outbreaks have occurred almost annually. In this study, we summarize available evidences on the epidemiology of WNV and West Nile neuro-invasive disease (WNND) in humans reported between 2012 and 2020. In total, 1145 WNV infection cases were diagnosed; of them 487 (42.5%) had WNND. A significant circulation of the pathogen was suggested by studies on blood donors, with annual incidence rates ranging from 1.353 (95% confidence intervals (95% CI) 0.279–3.953) to 19.069 cases per 100,000 specimens (95% CI 13.494–26.174). The annual incidence rates of WNND increased during the study period from 0.047 cases per 100,000 (95% CI 0.031–0.068) in 2012, to 0.074 cases per 100,000 (95% CI 0.054–0.099) in 2020, peaking to 0.377 cases per 100,000 (95% CI 0.330–0.429) in 2018. There were 60 deaths. Cases of WNND were clustered in Northern Italy, particularly in the Po River Valley, during the months of August (56.7%) and September (27.5%). Higher risk for WNND was reported in subjects of male sex (risk ratio (RR) 1.545, 95% CI 1.392–1.673 compared to females), and in older age groups (RR 24.46, 95% CI 15.61–38.32 for 65–74 y.o.; RR 43.7, 95% CI 28.33–67.41 for subjects older than 75 years), while main effectors were identified in average air temperatures (incidence rate ratio (IRR) 1.3219, 95% CI 1.0053–1.7383), population density (IRR 1.0004, 95% CI 1.0001–1.0008), and occurrence of cases in the nearby provinces (IRR 1.0442, 95% CI 1.0340–1.0545). In summary, an enhanced surveillance is vital for the early detection of human cases and the prompt implementation of response measures.

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Contrasted Epidemiological Patterns of West Nile Virus Lineages 1 and 2 Infections in France from 2015 to 2019

Pathogens ◽

10.3390/pathogens9110908 ◽

2020 ◽

Vol 9 (11) ◽

pp. 908 ◽

Cited By ~ 1

Author(s):

Cécile Beck ◽

Isabelle Leparc Goffart ◽

Florian Franke ◽

Gaelle Gonzalez ◽

Marine Dumarest ◽

...

Keyword(s):

Spatial Distribution ◽

West Nile Virus ◽

Invasive Disease ◽

Northern Italy ◽

Breaking Point ◽

Organ Donors ◽

West Nile ◽

Organ Donations ◽

History Of ◽

Lineage 2

Since 2015, annual West Nile virus (WNV) outbreaks of varying intensities have been reported in France. Recent intensification of enzootic WNV circulation was observed in the South of France with most horse cases detected in 2015 (n = 49), 2018 (n = 13), and 2019 (n = 13). A WNV lineage 1 strain was isolated from a horse suffering from West Nile neuro-invasive disease (WNND) during the 2015 episode in the Camargue area. A breaking point in WNV epidemiology was achieved in 2018, when WNV lineage 2 emerged in Southeastern areas. This virus most probably originated from WNV spread from Northern Italy and caused WNND in humans and the death of diurnal raptors. WNV lineage 2 emergence was associated with the most important human WNV epidemics identified so far in France (n = 26, including seven WNND cases and two infections in blood and organ donors). Two other major findings were the detection of WNV in areas with no or limited history of WNV circulation (Alpes-Maritimes in 2018, Corsica in 2018–2019, and Var in 2019) and distinct spatial distribution of human and horse WNV cases. These new data reinforce the necessity to enhance French WNV surveillance to better anticipate future WNV epidemics and epizootics and to improve the safety of blood and organ donations.

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