14 June 2007

West Nile virus

The United States Centers for Disease Control and Prevention reported on 22 May 2007 the first three confirmed cases of West Nile virus (WNV) in 2007. These occurred in the state of Mississippi [1]. As of 12 June 2007 there are three additional reported cases, one from Iowa, one from South Dakota and an additional case from Mississippi [1].

Advice for travellers

WNV is a mosquito-transmitted flavivirus; other flaviviral infections include yellow fever, dengue and Japanese encephalitis. Birds are the natural hosts of WNV, and the disease is transmitted to humans by several species of mosquitoes that mainly feed between dusk and dawn. There is no evidence of person to person transmission.

The majority of WNV infections (around 80%) are asymptomatic. Less than 20% will experience a mild, self-limited flu-like illness with fever, headache, myalgias, and rash. Less than 1% of those infected will develop a more severe neurological syndrome of meningitis and/or encephalitis. WNV infection is fatal in less than 1 out of 1,000 infections.

Health care professionals should be aware of the signs and symptoms of WNV and should obtain a detailed travel history from any suspected cases. Specialist advice should be sought when persons suspected of having WNV infection are evaluated, and specific testing can be performed at the Health Protection Agency (HPA).

Travellers should practice insect bite avoidance measures, in particular:

• Limit outdoor exposure during peak times of mosquito feeding - usually the hours from dusk to dawn.
• Wear loose-fitting, long-sleeved clothing and long trousers to prevent mosquito bites.
• Apply DEET-based insect repellents according to manufacturers' instructions to exposed skin, taking care to avoid eyes and mucous membranes.
• Clothing can be treated with a suitable insecticide solution.
• Indoor accommodation should be screened or air-conditioned.

References

1. Centers for Disease Control and Prevention. Division of Vector-borne Infectious Disease. West Nile Virus. Online resource. Accessed 14 June 2007. Available at: http://www.cdc.gov/ncidod/dvbid/westnile/

 

Links

Health Protection Agency Information on West Nile virus

http://www.hpa.org.uk/infections/topics_az/west_nile/default.htm

 

Public Health Agency of Canada

http://www.phac-aspc.gc.ca/wnv-vwn/index.html

 

NaTHNaC Clinical Update 17 May 2007. Insect bite avoidance measures – an update for the summer months.

http://www.nathnac.org/pro/clinical_updates

/biteavoidance_170507.htm