Abstract
West Nile virus (WNV) and Usutu virus (USUV) are two related arboviruses (genus Flavivirus, family Flaviviridae), with birds as a reservoir and mosquitoes as transmitting vectors. In recent years, WNV epidemiology changed in many European countries with increased frequency of outbreaks posing the issue of virus transmission risks by blood transfusion. USUV emerged for the first time in birds of the Tuscany region (Italy) in 1996 and in 2001 in Austria. While WNV is responsible for both mild and neuroinvasive diseases, USUV infection is usually asymptomatic and neuroinvasive symptoms are rare. Since WNV and USUV co-circulate, the surveillance of WNV allows also the detection of USUV. Due to the great similarity in amino-acid sequence of major surface proteins of the two viruses, a high cross-reactivity can lead to misinterpretation of serological results. Here, we report the results obtained from 54 asymptomatic blood donors during a three-year follow-up showing an unexpected high positivity (46.3%) for USUV. The major obstacle encountered in the differential diagnosis between these two viruses was the high cross-reactivity found in neutralizing antibodies (NT Abs) and, in some cases, a long follow-up was mandatory for a correct diagnosis. Moreover, two new ELISpot assays were developed for a more rapid and specific differential diagnosis, especially in those cases in which NT Abs were not determinant. Using a combination of Enzyme-linked immunospot (ELISpot), molecular, and serological tests, we could identify 25 true positive WNV and 25 true positive USUV blood donors. Our data highlight the importance of raising awareness for increasing USUV infections in endemic countries involved in blood transfusion and organ donation.
Highlights
West Nile virus (WNV) is an arbovirus, transmitted to humans by mosquito bite in a cycle in which different species of birds act as reservoir
The criteria to identify WNV true positive blood donors were as follows: (1) a positive WNV specific reverse transcriptase polymerase chain reaction (RT-PCR) and/or a positive WNV sequence in the pan-Flavivirus nested RT-PCRs independently from serological assay; (2) negative molecular tests but presence of specific WNV IgM, IgG, and neutralizing antibodies (NT Abs) without Usutu virus (USUV) Abs detection or without USUV NT Abs presence; (3) a four-fold increase in WNV NT Abs titer during the follow-up period compared to USUV titer in cross-reactive serum samples
Since WNV infection became a major problem in endemic areas, entomological surveillance and screening of blood donors were implemented in different regions in northern Italy [6]
Summary
West Nile virus (WNV) is an arbovirus (genus Flavivirus, family Flaviviridae), transmitted to humans by mosquito bite in a cycle in which different species of birds act as reservoir. From 2008, the increased number of WNV infections in humans in Emilia Romagna and Veneto regions led to the introduction of an integrated surveillance system for vectors and birds in order to rapidly identify WNV circulation and reduce the blood donor screening only to those areas in which the virus was circulating [4,5]. These preventive measures were rapidly extended in many Italian regions [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
