Epidemiological update: West Nile virus transmission season in Europe, 2016

Epidemiological update

Between June and November, ECDC publishes weekly epidemiological updates on West Nile fever human cases occurring in the European Union and neighbouring countries. The updates are available via the Surveillance Atlas of Infectious Diseases.

The epidemiological update includes neuro-invasive and non neuro-invasive autochthonous West Nile fever cases reported in the European Union and from neighbouring countries that meet the European Union case definition (Commission Decision 2008/426/EC). Cases detected by the European Union Member States are notified in real-time through The European Surveillance System (TESSy). Since 2016, Enlargement Countries are progressively reporting cases through TESSy. Cases in other neighbouring countries are detected via epidemic intelligence activities.

In 2016, 225 human cases of West Nile fever have been reported in the European Union: Romania (93), Italy (76), Hungary (44), Austria (5), Spain (3), Bulgaria (2), Cyprus (1) and Croatia (1). In the neighbouring countries, 267 cases have been detected: Russia (135), Israel (84), Serbia (41), Syria (2), Turkey (2), Egypt (1), Tunisia (1) and Ukraine (1).

In the European Union most cases were reported in Romania and Italy with respectively 41% and 34% of the European Union cases. Both Hungary and Romania reported a significant increase in number of cases compared to the 2015 transmission season. Romania notified 93 cases in 2016 compared to 32 in 2015 and Hungary notified 44 cases in 2016 compared to 22 in 2015. The number of West Nile fever cases in Italy was comparable with the previous season with 68 cases in 2016 compared to 61 in 2015. The first human case of West Nile fever ever detected in Cyprus was notified in August 2016 in the district of Larnaca. The case developed symptoms 18 days after returning from Greece. Investigations in both countries identified Cyprus as the most probable country of infection.  

Both Russia and Israel reported a large number of cases. Russia reported an increase in number of cases compared to the 2015 transmission season (135 cases in 2016 compared to 39 in 2015) while Israel observed a decrease (84 cases in 2016 compared to 125 in 2015). In 2016, West Nile virus infections were also reported from Syria and Egypt. The case infected in Egypt was reported by the French authorities. Although the exact place of infection could not be determined the two most likely places of infection were Cairo and Menoufia governorates.

The first human case of the West Nile fever 2016 season was notified on 20 June 2016 in Israel and in the European Union on 25 July 2016 by Italy. The last cases reported to TESSy during the 2016 transmission season in the European Union were reported by Italy on 21 November 2016 and by Israel in the neighbouring countries on 30 November 2016.

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West Nile virus infection

Most human infections are asymptomatic and the majority of clinical cases are mild and present with flu-like symptoms. In more severe cases there may be signs of encephalitis, meningo-encephalitis or meningitis.