Map credit – ECDC
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A dozen years ago the West Nile Virus (WNV) suddenly, and quite unexpectedly, appeared in New York City. And over the next few years it spread rapidly across the United States.
WNV is enzootic throughout much of Africa, parts of Europe, Asia and Australia.
Exactly how the virus was imported into the United States remains a mystery, although interhemispheric migration bird migration, birds carried by tropical storms, legal or illegal importation of birds from countries where the virus is endemic, or even infected mosquitoes hitching a ride on an international flight have been suggested as possibilities.
But no matter how it arrived, it flourished and spread.
From the USGS Factsheet on West Nile Virus
As you can see, the virus managed to rapidly expand its range during the first three years of its introduction into North America.
In 2002, however, the virus really exploded across the nation’s landscape.
Most people infected with WNV experience only mild, or sub-clinical symptoms. A very small percentage develop WNV neuroinvasive disease (WNND), a form of encephalitis.
For every serious presentation, there are probably 100 mild, or asymptomatic cases.
Last year, it turns out, was another banner year for West Nile Virus (WNV) cases in the United States, with 1,021 cases reported - up sharply over 2009 - and 62% of those producing neuroinvasive disease (i.e., meningitis, encephalitis, or acute flaccid paralysis) - Cite.
And in 2010 the West Nile Virus also made headlines in Europe; with Romania, Hungary, Italy, Spain and Greece all reporting human cases. In Greece, a large outbreak affecting the northern part of the country resulted in 262 human cases and 35 deaths being reported.
According, the ECDC now maintains an extensive West Nile Virus surveillance page and issues weekly updates and maps.
The latest update reads:
SITUATION UPDATE
As of 16 August 2011, a total of 21 confirmed human cases of West Nile fever have been reported in the EU (20 cases in Greece and 1 in Romania) and 26 in the neighbouring countries: 19 in the Russian Federation, 2 in Albania and 5 in Israel.
Between 09 and 16 August 2011, 14 new confirmed human cases have been reported from Greece, including 2 cases in new prefectures: Serres (1 case) and Trikala (1 case). In Attiki prefecture, all cases are still located in East Attica sub-prefecture.
- More information on West Nile infection in Greece is available from the Hellenic Center for Disease Control and Prevention website.
- Additional information on West Nile infection in horses in Greece, both in Attiki and Serres prefectures, is available from the World Organisation for Animal Health (OIE).
Since last week’s update, in the Russian Federation, ten new laboratory confirmed human cases have been reported from oblasts where cases occurred previously (Voronezhskaya and Volgogradskaya). In addition, three cases have been reported from an adjacent area, Rostovskaya oblast, for the first time this season.
In Albania, two cases have been reported in Lezhe prefecture. In Israel, 5 cases have been declared since June including two in the Northern district and two in Haifa district.
Yesterday the World Health Organization’s GAR (Global Alert and Response) network issued an advisory on the virus as well.
West Nile Virus Infection (WNV) in Europe
16 August 2011 - Laboratory confirmed cases of West Nile Virus infection (WNV) have been reported in a number of European countries. From the beginning of July 2011 to 11 August 2011, WNV infection has officially been reported by Albania (2 cases), Greece (22 cases) Israel (6 cases), Romania (1 case) and the Russian Federation (11 cases). The reporting reflects higher awareness among healthcare workers, enhanced laboratory capacities and favourable weather conditions with rainfall and high temperatures leading to a substantial increase in mosquitoes such as Aedes and Culex species.
The WHO Regional Office for Europe, together with key partners − such as the European Centre for Disease Prevention and Control (ECDC), the European Network for Diagnostics of “Imported” Viral Diseases (ENIVD) and the Network for Communicable Disease Control in Southern Europe and Mediterranean Countries (EpiSouth) − have been closely monitoring the regional situation of WNV.
WHO encourages the Member States to consider implementing relevant public health measures in order to minimize the impact of a potential WNV outbreak in countries at risk.
The WHO maintains a West Nile Virus fact sheet, which lists the following key facts.
- West Nile virus can cause a fatal neurological disease in humans.
- However, approximately 80% of people who are infected will not show any symptoms.
- West Nile virus is mainly transmitted to people through the bites of infected mosquitoes.
- The virus can cause severe disease and death in horses.
- Vaccines are available for use in horses but not yet available for people.
- Birds are the natural hosts of West Nile virus.
And it isn’t just WNV that Europe is concerned over. The mosquito vectors for Malaria, Dengue, Chikungunya, WNV, even Yellow Fever all are found in parts of the EU.
Increasingly, globalization, international travel and climate change are providing fresh opportunities for vector borne illnesses to spread to regions where they are not normally seen.
Given the rapid dissemination of the WNV in North America, it is understandable that the ECDC and the WHO are concerned, and are urging countries to get ahead of this virus before it becomes a larger threat.
