Abstract
Cases of West Nile Virus (WNV) disease were recorded for three consecutive years in Greece following the year 2010 outbreak. A cross-sectional serologic survey was conducted to estimate the WNV seroprevalence and assess the ratio of infection to neuroinvasive disease. A stratified left-over sampling methodology was used including age and residence strata. A total of 3,962 serum samples was collected and tested for WNV Immunoglobulin G (IgG) antibodies by Enzyme–Linked Immunosorbent Assay (ELISA). All positive samples were further tested by Plaque Reduction Neutralization Test (PRNT) and WNV Immunoglobulin M (IgM) antibodies. WNV IgG antibodies were detected in 82 samples and 61 were also positive in PRNT representing a weighted seroprevalence of 2.1% (95% C.I.: 1.7–2.6) and 1.5% (95% C.I.: 1.2–2.0), respectively. Multivariable analysis showed that seroprevalence was associated with age and residence. The overall ratio of neuroinvasive disease to infected persons was estimated at 1:376 (95% C.I.: 1:421–1:338), while the elderly people had the highest ratio. This nationwide study provided valuable data regarding the epidemiology of WNV in Greece based on the fact that elderly people have higher risk of being both infected and having severe disease.
Highlights
West Nile Virus (WNV) is considered to be one of the most important emerging arboviruses in recent years involving birds and by using Culex mosquitoes in its transmission cycle [1]
Information about gender, age, area of residence (NUTS-1 and prefecture) and result of Immunoglobulin G (IgG) seropositivity was provided for all participants
WNV IgG antibodies were detected in 82 samples while 61 were positive in Plaque Reduction Neutralization Test (PRNT) representing a weighted seroprevalence of: 2.1% (95% C.I.: 1.7–2.6) and 1.5% (95% C.I.: 1.2–2.0), respectively
Summary
WNV is considered to be one of the most important emerging arboviruses in recent years involving birds and by using Culex mosquitoes in its transmission cycle [1]. Outbreaks with severe symptoms have been reported in Europe (for example, Romania, Hungary, Italy, and Greece) in the last two decades [2,3,4,5]. In subsequent years, when the first detection of a strain of this lineage was reported from southeastern Hungary in 2004 [2], many reports of sporadic cases and outbreaks have occurred in various countries in Eastern Europe (Hungary, Russia, Romania), Southern Europe (Greece, Italy, Albania, Serbia) and the Middle East (Israel). One of the largest WNV disease outbreaks in Europe, took place in Greece in the year 2010; thereafter, similar WNV cases occurred every year during the transmission period (June to September). The first cases were reported in northern Greece (central Macedonia) near the city of Thessaloniki; the area is characterized by many wetlands, rivers and lakes that serve as stopping areas for migratory birds during their migration from overwintering areas in Africa to breeding sites in northern Europe and vice versa
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