BackgroundDespite the known circulation of West Nile virus (WNV) and Usutu virus (USUV) in Slovakia, no formal entomological surveillance programme has been established there thus far.AimTo conduct contemporaneous surveillance of WNV and USUV in different areas of Slovakia and to assess the geographical spread of these viruses through mosquito vectors. The first autochthonous human WNV infection in the country is also described.MethodsMosquitoes were trapped in four Slovak territorial units in 2018 and 2019. Species were characterised morphologically and mosquito pools screened for WNV and USUV by real-time reverse-transcription PCRs. In pools with any of the two viruses detected, presence of pipiens complex group mosquitoes was verified using molecular approaches.ResultsAltogether, 421 pools containing in total 4,508 mosquitoes were screened. Three pools tested positive for WNV and 16 for USUV. USUV was more prevalent than WNV, with a broader spectrum of vectors and was detected over a longer period (June-October vs August for WNV). The main vectors of both viruses were Culex pipiens sensu lato. Importantly, WNV and USUV were identified in a highly urbanised area of Bratislava city, Slovakias' capital city. Moreover, in early September 2019, a patient, who had been bitten by mosquitoes in south-western Slovakia and who had not travelled abroad, was laboratory-confirmed with WNV infection.ConclusionThe entomological survey results and case report increase current understanding of the WNV and USUV situation in Slovakia. They underline the importance of vector surveillance to assess public health risks posed by these viruses.

• Keywords
• Europe, Slovakia, Usutu, West Nile, arbovirus, flavivirus, mosquitoes,
• MeSH
• Culex * MeSH
• Culicidae * MeSH
• Flavivirus * genetics   MeSH
• Humans MeSH
• West Nile virus * genetics   MeSH
• West Nile Fever * diagnosis   epidemiology   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Case Reports MeSH
• Geographicals
• Slovakia epidemiology   MeSH

Monitoring West Nile virus (WNV) and Usutu virus (USUV) activity now has the highest priority among mosquito-borne pathogenic viruses circulating in the European Union. This study documents a first time detection and the co-circulation of WNV lineage-2 (with the minimal prevalence of 0.46%) and USUV clade Europe 2 (with the minimal prevalence of 0.25%) in mosquitoes from the same habitat of south-western Slovakia and underlines necessity to perform rigorous surveillance in birds, mosquitoes, horses and humans in that country.

• Keywords
• Culex spp., Usutu virus, West Nile fever, West Nile virus, mosquitoes, surveillance,
• MeSH
• Culex virology   MeSH
• Culicidae virology   MeSH
• Ecosystem MeSH
• Flavivirus genetics   isolation & purification   MeSH
• Phylogeny MeSH
• Flavivirus Infections epidemiology   veterinary   MeSH
• Mosquito Vectors virology   MeSH
• Horses virology   MeSH
• Humans MeSH
• Prevalence MeSH
• Birds virology   MeSH
• Public Health MeSH
• West Nile virus genetics   isolation & purification   MeSH
• West Nile Fever epidemiology   veterinary   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Slovakia epidemiology   MeSH