The National Disease Surveillance Centre (NDSC) has issued a travel advisory to people visiting the US and Canada in late summer and autumn, asking them to be vigilant about infection with the West Nile Virus.
The disease, which first appeared in north America in 1999, is transmitted to humans through the bite of an infected mosquito. West Nile Virus is carried from infected birds to humans by mosquitoes. It cannot be directly transmitted between humans.
There have been no reported cases of the disease in the Republic or Britain.
Dr Paul McKeown, a specialist in public health medicine at the NDSC, said yesterday that while the risk of infection was small it was important for travellers to be aware of the condition.
"Four out of five people who are bitten by a mosquito will have no symptoms at all, while about 20 per cent will develop a mild flu-like illness.
"Less than 1 per cent develop more severe disease which produces headache, high fever, stiff neck and sore eyes," he said.
In the rare event of the brain tissue itself becoming inflamed (encephalitis), symptoms include muscle weakness, disorientation, convulsions and coma.
The risk of developing a severe version of West Nile Virus increases with age; people over the age of 50 are 10 times more likely than children and young people to develop severe symptoms.
Last year, there were over 4,000 cases of the virus in the United States; 284 of these died from complications of the disease. Canada reported 400 cases of West Nile Virus in 2002.
There is no specific treatment for the disease. Researchers are working on a vaccine. Mild cases of the virus recover within three to six days with simple treatment such as paracetamol, rest and fluids. In severe infection, hospitalisation and intensive care treatment is required.
Prevention is the key to avoiding infection. Travellers should take the following steps:
Wear protective clothing (long sleeves, long trousers and socks) when mosquito exposure is likely;
Use an insect repellent containing DEET (N-diethyl-m-toluamide) on exposed skin when outdoors;
Stay indoors at dawn and dusk when mosquitoes are most active;
Use screens, nets and where available, air conditioning, when indoors;
Avoid areas with standing water (mosquito breeding grounds) such as bird baths, ponds and stagnant pools.