Abstract
Human cases of West Nile virus (WNV) disease have been reported in Italy since 2008. So far, most cases have been identified in north-eastern Italy, where, in 2012, the largest outbreak of WNV infection ever recorded in Italy occurred. Most cases of the 2012 outbreak were identified in the Veneto region, where a special surveillance plan for West Nile fever was in place. In this outbreak, 25 cases of West Nile neuroinvasive disease and 17 cases of fever were confirmed. In addition, 14 WNV RNA-positive blood donors were identified by screening of blood and organ donations and two cases of asymptomatic infection were diagnosed by active surveillance of subjects at risk of WNV exposure. Two cases of death due to WNND were reported. Molecular testing demonstrated the presence of WNV lineage 1 in all WNV RNA-positive patients and, in 15 cases, infection by the novel Livenza strain was ascertained. Surveillance in other Italian regions notified one case of neuroinvasive disease in the south of Italy and two cases in Sardinia. Integrated surveillance for WNV infection remains a public health priority in Italy and vector control activities have been strengthened in areas of WNV circulation.
Highlights
West Nile virus (WNV), a mosquito-borne flavivirus of the Japanese encephalitis sero-complex, is an emerging pathogen that is causing disease in humans in Europe and worldwide [1]
In 2012, most human cases of WNV infection occurred in north-eastern Italy, in areas that had been affected in 2010 and 2011 (Figure 1) [13,23,35]
In 2012, a markedly higher incidence of WNV infection was observed than in previous years, with 25 cases of WNND, 17 cases of WNF, 14 WNV RNA-positive blood donors, and further two cases of asymptomatic WNV infection identified by active surveillance of subjects at risk of WNV exposure
Summary
West Nile virus (WNV), a mosquito-borne flavivirus of the Japanese encephalitis sero-complex, is an emerging pathogen that is causing disease in humans in Europe and worldwide [1]. While in 2008–2010 human cases of infection were detected only in northeastern Italy and were caused by WNV lineage 1 genotypes [28,29,30,35], in 2011, in addition to northeastern Italy [23], cases were notified for the first time in Marche region (Central Italy) and in Sardinia island and included infections with WNV lineage 2 [25,36] These epidemiological data show that Italy is at risk for the occurrence of WNV outbreaks and indicate the importance of having in place surveillance programs for WNV infection in areas at risk. This outbreak as well as other cases of human infection were identified in Italy in 2012 by the national surveillance plan, and are described in this report
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