West Nile virus and other mosquito-borne viruses present in Eastern Europe

Abstract

Eastern Europe (EE) has been severely affected by mosquito-borne viruses (moboviruses). In this review, we summarize the epidemiology of moboviruses, with particular attention to West Nile virus (WNV). The study of WNV human cases in EE between 2010 and 2016, revealed that the epidemiology of WNV in EE is complex with the combination of introduction of different WNV strains from lineages 1 and 2, and the establishment of endemic cycles. We found a positive correlation between the risk of WNV re-emergence in an area and the number of human cases reported in the previous year. We also report the main ecological and biological characteristics of the key mosquito species vectors of moboviruses. Recent expansion of invasive mosquito species in EE, mainly Aedes albopictus but also Aedes aegypti and Culex quinquefasciatus, may result in new scenarios with an increased risk of transmission of moboviruses. Main gaps of knowledge in relation to moboviruses and their vectors in EE are identified. Understanding the epidemiology of moboviruses in EE is essential for the improvement of their surveillance and the control of the diseases they cause.

Keywords: Culex and Aedes mosquito; Eastern Europe; Mosquito-borne viruses; West Nile virus.

Figure 1.

Distribution of the different moboviruses in the EE countries included in the study: West Nile virus (WNV), Usutu virus (USUV), Dengue virus (DENV), Bunyamwera orthobunyavirus (BUNV), California encephalitis virus (CEV), Turlock orthobunyavirus (TURV), Rift Valley fever phlebovirus (RVFV) and Sindbis virus (SINV).

Figure 2.

Cases of human WNV-infections registered by the ECDC in the countries under study for each year between 2010 and 2016. Distribution of cases is only an approximation as the location is randomly generated within the minimum geographical unit available in the ECDC data (NUTS3 level or equivalent unit for non-EU countries). Official outbreaks in horses reported through the EU Animal Disease Notification System (ADNS) and collected to the RASVE system of the Spanish Ministry of Agriculture, Fisheries, Food and Environment are also represented.

Figure 3.

In dark red dates when reporting of new cases start for different countries and years. In orange, period between first and last report for that country and year (proxy of the period of WNV transmission). Only the first case in each area is available in the ECDC tables, so the actual date of the last case may be later than reported in the figure.