Seroprevalence of West Nile virus antibodies in blood donors living in the metropolitan area of Milan, Italy, 2009-2011.

A seroprevalence study for anti-West Nile virus-specific antibodies was carried out in healthy blood donors resident in the metropolitan area of Milan in two different years, 2009 and 2011. In 2009 no positive sera were found, whereas 5 positive sera were found in 2011, revealing viral circulation in this naive area. The seroprevalence rate identified in 2011 was 0.57%, suggesting that the area of WNV circulation in Italy is larger than that previously identified.