5 October 2012
West Nile virus: advice for travellers to USA, Europe and neighbouring countries
West Nile virus
West Nile virus (WNV) is a viral illness of humans and birds transmitted by Culex spp mosquitoes. Human infections can be asymptomatic or can vary in severity from mild symptoms to neurological illness including meningitis or encephalitis.
Since being introduced into the United States (US) in 1999, WNV has been reported from almost every state. In 2011, a total of 721 cases were reported from 43 states and the District of Columbia [1,2]. During 2012, as of 2 October, 3,969 cases of human WNV have been reported to the US Centers for Disease Control and Prevention, including 163 deaths. This is the highest number of cases and deaths reported in USA since 2003 .
Almost 70 per cent of the cases have been reported from eight states (Texas, California, Louisiana, Mississippi, South Dakota, Michigan, Oklahoma, and Illinois) .
Texas has reported the highest number of cases for an individual US state in 2012, accounting for a third of all cases reported in the US. As of 3 October, 1,438 cases in 116 of the counties of Texas have been reported, with most cases residing in Dallas, Tarrant, Denton and Travis counties [1, 3]. In 2011, there were 27 reported cases with 2 deaths; the highest number of human cases in Texas was recorded in 2006 (454 cases with 33 deaths) .
Europe and neighbouring countries
Outbreaks and sporadic cases of human WNV infection have occurred in Europe since the 1950s. WNV has been reported over the years from many other areas of the world, including Africa, Asia, Australia and Middle East. The complete list of countries currently affected by WNV can be found on the European Centre for Disease Prevention and Control website [5-7].
As of 4 October 2012, the highest recorded activity is currently in the Russian Federation (379 cases), Greece (154), Israel (46), Serbia (45) and Italy (38 cases) .
In 2012, human cases of WNV have been reported in Kosovo for the first time. As of 4 October 2012, three regions of Kosovo have reported cases: Kosovski (two cases), Kosovsko-Pomoravski (one case) and Prizremski region (one case) .
Advice for travellers
WNV is transmitted to humans by the bite of a mosquito. Cases in returned UK travellers are rare. However, all travellers should practise insect bite avoidance measures when visiting countries where WNV is reported. Culex spp mosquitoes bite during the evening and night .
Advice for health professionals – the returned traveller
A diagnosis of WNV infection should be considered in patients presenting with neurological syndromes, or with other compatible symptoms, especially in those who have a recent history of travel to countries where WNV is known to be circulating. Relevant samples for testing together with a full clinical and travel history should be submitted to the Health Protection Agency Rare and Imported Pathogens Laboratory.
1. U.S Centers for Disease Control and Prevention. 2012 West Nile Virus update. 2 October 2012. [Accessed 5 October 2012]. Available at: http://www.cdc.gov/ncidod/dvbid/westnile/index.htm
2. U.S Centers for Disease Control and Prevention. West Nile Virus (WNV) activity reported to ArboNET, by state, United States, 2012. as of 3 October, 2012. [Accessed 5 October 2012]. Available at: http://www.cdc.gov/ncidod/dvbid/westnile/Mapsactivity/surv
3. Texas Department of State Health Services. West Nile Virus in Texas. 3 October 2012. [Accessed 5 October 2012]. Available at: http://www.dshs.state.tx.us/idcu/disease/arboviral/WestNile/
4. Texas Department of State Health Services. Human West Nile Virus cases Texas 2002-2011. 13 August 2012. [Accessed 5 October 2012]. Available at: http://www.dshs.state.tx.us/idcu/disease/arboviral/west
5. Hubalek Z, Halouzka J. West Nile Fever – a re-emerging Mosquito-borne viral disease in Europe. Emerg Inf Dis 1999:5:643-650.
6. European Centre for Disease Prevention and Control. West Nile Fever maps, 4 October 2012. [Accessed 5 October 2012]. Available at: http://ecdc.europa.eu/en/healthtopics/west_nile_fever/West-Nile-fever-maps/Pages/index.aspx
7. Field VF, Ford L, Hill DR eds. Health Information for Overseas Travel, National Travel Health Network and Centre, London, UK, 2010.
8. The Ill Returned Traveller Ch. 4.2 In: Field VF, Ford L, Hill DR (Eds). Health Information for Overseas Travel. National Travel Health Network and Centre. London, UK. 2010.
ECDC website: West Nile virus
ECDC website: West Nile fever maps
HPA website: West Nile virus