The Health Protection Agency starts surveillance programme for human cases of West Nile virus infection

May 27 2004

The Health Protection Agency is starting its annual enhanced surveillance programme for possible human cases of West Nile virus infection. The scheme, which has been used for the last three years, operates during the summer, when there is West Nile virus activity in other countries.

Dr Dilys Morgan who coordinates the scheme for the Agency, said, “Our surveillance scheme involves looking for West Nile virus in blood and cerebrospinal fluid samples, taken from patients with encephalitis or viral meningitis with no known cause. This includes those who have recently returned from areas where there is West Nile Virus activity, and where mosquitoes which could potentially transmit the disease are most active. We are requesting that clinicians and laboratories refer these samples to HPA Porton Down, who will carry out laboratory investigations.

“West Nile virus is an infection which in the last three years has had a significant impact in the United States. The virus is spread from birds to humans via mosquito bites. Symptoms include headache, fever and disorientation, and the disease can cause serious illness in a small percentage of infected people. The UK is thought to be at low risk for human cases of West Nile Virus and to date, our surveillance has found no human cases in the UK, either amongst residents here or in people who have travelled to the US. The UK is not affected by mosquito-borne disease to the extent that the US is; indeed transmission of mosquito-borne viral infections in the UK is rare.

“The Agency, however, takes the potential threat to the UK seriously, and so advice is issued to doctors to consider West Nile virus as a possible diagnosis for unexplained cases of encephalitis and viral meningitis, to refer samples accordingly, and to be aware of the situation in the US.”

The Agency has been working with the Department of Health on its West Nile Virus Contingency Plan, which will be issued shortly. The Agency also has advice on its website for travellers to the US, on how to minimise the risk of contracting West Nile virus. This advice includes sensible precautions to prevent insect bites, such as using an effective insect repellent and installing insect-proof screens on windows and doors.