9 October 2007

Eastern equine encephalitis virus in a UK traveller

A 35-year patient suffering from Eastern Equine Encephalitis (EEE) is seriously ill and receiving treatment in the Western General Hospital, Edinburgh, according to the Lothian NHS Board [1]. During the summer of 2007 he visited family and friends in Rhode Island and New Hampshire in the United States (US) and spent time fishing. This is the first case of EEE in a European traveller.

Eastern equine encephalitis

EEE is a mosquito borne virus which mainly affects birds and occasionally horses.  Cases in humans are extremely rare [2]. Between 1964 and 2006 approximately 220 confirmed cases were reported in the whole of the US, which is approximately five cases a year. Most cases occur in the eastern and south-eastern states of the US, predominantly Florida, Georgia, Massachusetts and New Jersey. In Rhode Island and New Hampshire (where the Scottish case had travelled), five and eight cases respectively were reported [3,4]. Transmission is most likely in freshwater hardwood swamps, which are breeding grounds for the vector mosquitoes. However as the colder weather sets in the risk at this time of year will decrease. There is no vaccine available for use in humans; prevention relies on insect bite avoidance which is of paramount importance. EEE does not occur in the United Kingdom.

Advice for travellers

EEE is a rare disease in travellers. There are a number other diseases transmitted by insects in the USA which pose a larger risk  such as West Nile disease. Travellers concerned about insect borne diseases should contact their general practitioner/practice nurse or specialist travel clinic, or consult the NaTHNaC Country Information Pages for specific advice. All travellers to areas where mosquito and other insect borne diseases are prevalent, including the USA are advised to take insect bite avoidance measures.

References

1. Health Protection Scotland. Weekly Report: Eastern Equine Encephalitis, 2007. Vol 41, No. 40. Available at: http://www.documents.hps.scot.nhs.uk/ewr/pdf2007/0740.pdf

2. Centers for Disease Control. Arboviral Encephalitides; Eastern Equine Encephalitis Fact Sheet 2006; 12 July. Available at:

http://www.cdc.gov/ncidod/dvbid/arbor/eeefact.htm

3. Centers for Disease Control. Eastern Equine Encephalitis Cases in Humans, 1964-2006; Updated 7.6.07. Accessed 8.10.07. Available at:

http://www.cdc.gov/ncidod/dvbid/arbor/images/EEE_Map.jpg

4. Centers for Disease Control. Confirmed and probable cases of Eastern Equine Encephalitis, Human, United States 1964-2006, By State. Updated 7.6.07. Accessed 8.10.07. Available at: http://www.cdc.gov/ncidod/dvbid/arbor/pdf/EEE_%20DOC.pdf