Epidemiological update: End of West Nile virus transmission season in Europe, 2014

Epidemiological update

​The West Nile virus transmission period in the EU is drawing to a close. No recent cases have been reported since 31 October in European countries, and active mosquito populations are decreasing. ECDC is therefore ending its seasonal monitoring of the West Nile virus transmission.

Since 5 June 2014, ECDC has published on its website weekly updates on spatial distribution of West Nile fever cases in the European Union and neighbouring countries. Cases reported in the EU—autochthonous human West Nile fever cases (neuro-invasive and non neuro-invasive), meeting laboratory criteria as per the EU case definition (Directive 2008/426/EC)—and all reported cases outside the EU, are shown on the maps. The first cases of West Nile fever (2 cases) were reported on 13 June 2014 from Republika Srpska in Bosnia and Herzegovina. These cases occurred after cyclone Tamara that caused severe floods in the country as well as in Croatia and Serbia.

As of 20 November 2014, 74 human cases of West Nile fever (including 66 neuro-invasive infections) were reported in the EU; one case in Austria, 15 in Greece, 11 in Hungary, 24 in Italy and 23 in Romania. In neighbouring countries, 136 cases were detected in Bosnia and Herzegovina, Israel, Palestine*, Serbia and the Russian Federation.

In the EU, the highest numbers of cases have been reported in Italy and Romania. However, considering the affected territory, Romania and Hungary have been the most affected countries as 25% of the Romanian districts and 23% of the Hungarian counties, including the capitals of both countries, have reported cases.

In Greece, the transmission was limited to four prefectures including the capital and only 15 cases were reported even though enhanced surveillance has been in place in the country during the whole transmission season. For the first time, Austria reported one case in Wien (Vienna) city. This case was detected through the systematic screening of blood donation that was implemented this year after three cases were retrospectively identified in the greater Vienna area in 2009 and 2010.

All these cases detected in the EU have been reported into TESSy through the real time reporting system implemented since this year for all EU countries.

In the neighbouring countries, most of the cases were reported from Serbia where 76 cases were detected in nine districts, including the capital, Grad Beograd. Both the number of cases and number of affected districts are much lower this year than last year (18 districts affected and 302 cases reported in 2013).

The number of reported cases is also lower this year in Israel (17 cases versus 63 in 2013) and in the Russian Federation (29 cases versus 177 cases in 2013).

Finally, Bosnia and Herzegovina reported 13 cases and was the first country to report cases this year. With Serbia and Croatia, Bosnia and Herzegovina experienced huge floods at the beginning of the West Nile fever transmission season but all countries implemented control measures to reduce mosquito populations.

Since 31 October, no recent cases have been reported in European countries. With the decrease of mosquito populations’ activity, the season of West Nile virus transmission to humans is now coming to an end in the EU and neighbouring countries. ECDC published its last weekly update of the WN fever maps on Friday 20 November closing its seasonal monitoring of West Nile virus transmission for 2014.

See the West Nile fever maps.

*This designation shall not be construed as recognition of a State of Palestine and is without prejudice to the individual positions of the Member States on this issue.