WNV >  Information for Healthcare Professionals > Epidemiology
Worldwide epidemiology:

Since the first isolation of WNV in 1937 in Uganda and until 1999, sporadic cases and outbreaks had been reported: during early 1950s in Egypt, in the 1960s in France and in the 1970s in South Africa.

In North America, the first emergence of the disease took place in New York City during the summer of 1999, and it was soon spread across other states in the following years.

In Asia, outbreaks occasionally occurred in southern regions and especially in India, while sporadic cases were reported in Southeast Asia.

In Australia, Kunjin virus, considered to belong to a sublineage of WNV has caused a total of 13 human cases during the period from 1992 to 2010.

In Europe, the first large-scale epidemic took place in 1996 in Romania.

Especially concerning Europe, the year 2010 was characterized by epidemics in several countries (Figure 1) such as Greece, Romania, Hungary, Italy and Spain, while a quite large outbreak occurred in Russia, and human cases were recorded in Turkey for the first time. 

Figure 1

In 2011, 130 cases were reported in of European Union (EU)  member states (100 cases in Greece, 16 in Italy, 11 in Romania, 3 in Hungary) and 207 in neighbouring countries (Albania, FYROM, Israel, Russian Federation, Tunisia, Turkey and Ukraine).

Figure 2

Epidemiology in Greece:

In summer 2010, WNV was detected in Greece for the first time. Until November 2010, 262 cases were reported; 197 of them displayed a WNV neuroinvasive disease (WNND; involvement of nervous system, e.g. meningitis, encephalitis, etc), while 65 were non-neuroinvasive cases with mild symptoms (mainly fever). The largest number of WNND was recorded in Central Macedonia (districts of Imathia, Kilkis, Thessaloniki, Serres). The case fatality rate of the WNND cases was 17,7%, while a total of 35 deaths were recorded in elderly people who had underlying disease.

In early summer 2011, one month after the seroconversion observed in sentinel chicken, the first human WNV case was diagnosed, indicating the onset of the 2011 epidemic. That year, Thessaly (Central Greece) was more affected than Central Macedonia, while a little later human cases were recorded also in East Attica. The total number of cases that were reported was 100, out of which 75 were WNND and 25 with mild symptoms (not including an imported case), while the case fatality rate for the WNND was 12% with 9 deaths observed in persons over the age of 65. Figure 3 shows the WNV human cases in Greece during 2010-2011.

Figure 3. West Nile virus human cases in Greece, 2010-2011

In 2012, the total number of reported cases was 161 (Figure 4); 109 of them were WNND (including a case diagnosed in Germany but was in Greece during incubation period), while 52 were cases with mild symptoms. Eighteen (18) deaths were recorded. In addition, two imported cases from the USA were reported.

Figure 4. West nile virus human cases in Greece, 2012

Epidemiological situation in Greece - 2013

Until 06/11/2013, 86 cases have been reported; 51 of them with Central Nervous System manifestations, while 9 deaths have been recorded. 

For more information, follow the link:

HCDCP_Weekly Epidemiological Report for West Nile virus in Greece_06_11_13

Epidemiological situation in Greece - 2014

Until 25/09/2014, 15 cases have been reported; 14 of them with Central Nervous System manifestations, while 5 deaths have been recorded in elders. 

For more information, follow the link:

HCDCP_Weekly Epidemiological Report for West Nile virus in Greece_25_09_14

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