AIM: To analyse repeated detection of West Nile virus (WNV) in mosquitoes in South Moravia in correlation with the first documented autochthonous human cases of West Nile fever (WNF), focusing on epidemiological and environmental investigation. MATERIALS AND METHODS: Here we report case studies of five patients with autochthonous WNF without any travel history diagnosed in South Moravia in 2018, along with in-depth epidemiological and environmental investigation. The cases were classified as confirmed based on the case definition criteria established in Commission Implementing Decision (EU) 2018/945. RESULTS: Between July and September 2018, a total of five human cases of West Nile virus infection were suspected and subsequently confirmed by the National Reference Laboratory for Arboviruses in Ostrava. All mosquito suspensions from the area where the first case of WNV infection was diagnosed tested WNV negative. CONCLUSIONS: WNV circulation in South Moravia has been known since 1997 when the first human cases (probably caused by WNV lineage 1) were confirmed after floods. The presence of more serious neuroinvasive lineage 2 (WNV-2), now circulating in central and eastern Europe, was detected repeatedly in 2013, 2015, and 2016 in Cx. modestus and Cx. pipiens mosquitoes within the scope of targeted entomological surveillance. These findings were published in 2016-2018 in both the professional press and mass media. It was only a matter of time and of making the correct differential diagnosis in patients with non-specific neuroinfections before there were confirmed autochthonous human cases of WNF caused by WNV-2. These presumptions were corroborated by epidemiological investigations performed by the staff of the Regional Public Health Authority of the South Moravian Region and Academy of Sciences.

History of Arbovirus Research in the Czech Republic