engleski

Usutu virus infections in Croatia: five years later

Usutu virus (USUV) is a mosquito-borne arbovirus that belongs to the family Flaviviridae, genus Flavivirus. Birds are the natural reservoirs of virus and mosquitoes of the genus Culex are the main vectors. Although human clinical cases were rarely reported, recent data from Italy showed that USUV infections may be more frequent than WNV infections in regions where both viruses co- circulate. The aim of this study was to present the occurrence, clinical symptoms and molecular epidemiology of USUV infections detected in Croatia. USUV was confirmed by detection of specific antibodies using ELISA and virus neutralization test (VNT) and/or detection of USUV RNA using RT-PCR. RT-PCR positive samples were further tested using Sanger sequencing. In Croatia, the first USUV seropositive human was detected in 2012. So far, six cases of human USUV neuroinvasive disease were confirmed. Three cases were detected in 2013 and three cases in 2018 transmission season, five years after the first ones. In five patients, infection was confirmed by detection of USUV neutralizing antibodies, while in one fatal case, USUV RNA was detected in a urine sample. Patients were from Zagreb/Zagreb County, Požega-Slavonia and Osijek-Baranja County. Two USUV seropositive horses were recorded 2011 in Zagreb and Sisak-Moslavina County. During the 2018 outbreak, USUV was for detected the first time in one dead blackbird (Turdus merula) from Zagreb County. USUV positive mosquito pools were recorded in 2016 (Aedes albopictus ; Zagreb), 2017 (Culex pipiens ; Međimurje County) and 2018 (Cx. pipiens ; Zagreb). Sequence was obtained from pooled Cx. pipiens sample collected in 2018. Phylogenetic analysis showed that Croatian strains detected in human, blackbird and Cx. pipiens pool belong to USUV Europe 2 lineage. Our results confirm the presence of USUV in Croatia. Further studies are needed to analyze the clinical significance as well as distribution of this emerging arboviral infection.

Usutu virus ; epidemiology ; Croatia

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