The World Health Organisation has warned that potentially fatal West Nile virus is rapidly spreading across European countries popular with British holidaymakers.
Officials are urging tourists and locals to take precautions to avoid mosquito bites, as the insects acquire the disease by feeding on infected birds. There is no licensed vaccine for humans and no specific antiviral drugs, with care limited to managing symptoms and supportive hospital treatment for severe cases affecting the central nervous system. The virus can cause high fever, neck stiffness, disorientation, tremors, convulsions, muscle weakness, paralysis or coma.
Greece has recorded the steepest recent rise, with 21 human cases confirmed by national health authorities as of July 22, including 14 in the past week alone. Twenty of the 21 patients developed neuro-invasive disease, including encephalitis or meningitis, and 13 remain hospitalised.
Italy has the widest geographic spread, with 21 cases confirmed across 17 separate areas as of July 15, the latest data available. Multiple locally acquired human cases have also been reported in Spain, Romania and North Macedonia.
How the virus spreads
Most people catch the disease through the bite of an infected mosquito, although transmission through organ transplant, blood transfusion, pregnancy and breastfeeding has also been documented. The WHO said that for most people the risk remains low, but anyone living in or travelling to an affected area should take basic steps to avoid mosquito bites and know the signs of severe illness.
In Europe, most human infections occur during mosquito season, typically from late spring through autumn, with the highest transmission usually seen between July and September.
Dr Hans Henri P Kluge, WHO regional director for Europe, said West Nile virus is not a new threat, but the conditions that make it spread are changing rapidly. He said warmer temperatures and longer summers are giving mosquitoes more time and territory to transmit the virus. Kluge said most infections are mild, but roughly 1 in 150 people who contract it will develop a severe infection affecting the central nervous system that can be life-threatening. He said simple steps like covering up, using insect repellent, and clearing stagnant water around the home can make a real difference, and that anyone who develops a high fever, rash or neck stiffness after a mosquito bite should see a doctor without delay.
Symptoms and treatment
Between 70 and 80 per cent of people with West Nile virus infection will not develop any symptoms. Those who do may experience fever, headache, tiredness, body aches, nausea or vomiting, and sometimes a rash or swollen lymph glands.
The WHO said anyone developing symptoms after returning from an area where the virus is circulating should seek medical care promptly, while those with severe symptoms should do so immediately. Care focuses on rest, fluids, pain relief and, in severe cases, hospital-based supportive treatment. Infection can be confirmed through laboratory testing, including detection of virus-specific antibodies or viral RNA, depending on the timing of illness.
Prevention advice
The WHO Regional Office for Europe is urging countries to strengthen mosquito surveillance and public knowledge of protective measures. It advises wearing light clothing covering most of the body, including long sleeves and trousers, using mosquito repellent containing approved active ingredients, and limiting time outdoors at dawn and dusk, when mosquitoes are most active.
Windows and doors should be fitted with screens to keep mosquitoes out of the home, with mosquito nets over beds and babies' cots. Stagnant water, a common breeding site, should be removed from around the home and in public places, the WHO added.
