Abstract
BackgroundDuring the 2018 WNV transmission season, similarly to other endemic areas in Europe, a large number of human West Nile virus (WNV) infections were reported in Hungary.AimsWe summarise the epidemiological and laboratory findings of the 2018 transmission season and expand experiences in flavivirus differential diagnostics.MethodsEvery patient with clinical suspicion of acute WNV infection was in parallel tested for WNV, tick-borne encephalitis virus and Usutu virus (USUV) by serological methods. Sera, whole blood and urine samples were also tested for the presence of viral nucleic acid.ResultsUntil the end of December 2018, 215 locally acquired and 10 imported human WNV infections were notified in Hungary. All reported cases were symptomatic; most of them exhibited neurological symptoms. In a large proportion of tested individuals, whole blood was the most appropriate sample type for viral nucleic acid detection, but because whole blood samples were not always available, testing of urine samples also extended diagnostic possibilities. In addition, the first human USUV infection was confirmed in 2018 in a patient with aseptic meningitis. Serological cross-reactions with WNV in different serological assays were experienced, but subsequent molecular biological testing and sequence analysis identified Europe lineage 2 USUV infection.ConclusionCareful interpretation and simultaneous application of different laboratory methods are necessary to avoid misdiagnosis of human USUV cases. Expansion of the laboratory-confirmed case definition criteria for detection of viral RNA in any clinical specimens to include urine samples could increase diagnostic sensitivity.
Highlights
During the 2018 WNV transmission season, to other endemic areas in Europe, a large number of human West Nile virus (WNV) infections were reported in Hungary
Until 2008, WNV infections had been reported in Hungary only within the syndromic surveillance system, as aseptic meningitis and/or infectious encephalitis
In 2018, the first locally acquired human WNV infection was diagnosed during week 28, with symptom onset in week 27, much earlier than generally in previous years (Figure 1)
Summary
During the 2018 WNV transmission season, to other endemic areas in Europe, a large number of human West Nile virus (WNV) infections were reported in Hungary. Methods: Every patient with clinical suspicion of acute WNV infection was in parallel tested for WNV, tick-borne encephalitis virus and Usutu virus (USUV) by serological methods. West Nile virus (WNV) and Usutu virus (USUV) are phylogenetically closely related mosquito-borne members of the family Flaviviridae, and belong to the Japanese encephalitis antigenic complex of the Flavivirus genus [1,2]. Both viruses have been isolated from numerous ornithophilic mosquito species, mainly Culex spp. Additional transmission routes of human WNV infection including occupational transmission in laboratory settings, transplacental transmission and transmission via breast milk or during delivery have rarely been described [8,9,10,11]
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