The WHO Regional Office for Europe is urging countries to strengthen mosquito surveillance and public knowledge of protective measures as West Nile virus cases climb in parts of the continent, with the transmission season just getting under way. For most people, the risk remains low, but anyone living in or travelling to an affected area should take basic precautions to avoid mosquito bites and be aware of the signs of severe illness in case they or someone close to them falls ill
Current situation
Greece has recorded the steepest recent rise, with 21 human cases confirmed by national health authorities as of 22 July, 14 of them in the preceding week alone. Twenty of the 21 patients developed neuroinvasive disease, including encephalitis or meningitis, and 13 remain hospitalized. Italy has the widest geographic spread, with 21 cases confirmed in 17 separate areas as of 15 July. Locally acquired human cases have also been reported in North Macedonia (2), Romania (2) and Spain (2)
Mosquito-borne infection
West Nile virus is transmitted through the bite of an infected mosquito. In Europe, most human infections occur during the mosquito season, typically from late spring through autumn, with the highest transmission usually observed between July and September. There is no licensed vaccine for humans and no specific antiviral treatment. Treatment is limited to managing symptoms and supportive care in hospital for severe cases
“West Nile virus is not a new threat, but the conditions driving its spread are changing rapidly,” said Dr Hans Henri P. Kluge, WHO Regional Director for Europe. “Warmer temperatures and longer summers are giving mosquitoes more time and territory to transmit this virus. Most infections are mild, but roughly 1 in 150 people who contract the virus will develop a severe infection affecting the central nervous system, which can be life-threatening. Simple steps like covering up, using insect repellent and clearing stagnant water around the home can make a real difference. Anyone who develops a high fever, rash or neck stiffness after a mosquito bite should see a doctor without delay.”
Mosquitoes acquire the West Nile virus by feeding on infected birds and pass it to humans and other animals through bites. Transmission through organ transplantation, blood transfusion, pregnancy and breastfeeding has also been documented, though rarely. No human-to-human transmission through everyday contact has ever been recorded
Protecting against infection
WHO/Europe recommends the following measures to reduce the risk of mosquito bites
- Wear light clothing covering most of the body, including long sleeves and trousers.
- Limit time outdoors at dawn and dusk, when mosquitoes are most active.
- Fit window and door screens to keep mosquitoes out of the home.
- Apply mosquito repellent containing approved active ingredients, according to the manufacturer’s instructions. An adult should apply repellent to young children and avoid applying it to their hands or around the eyes and mouth.
- If possible, sleep in an air-conditioned room, use fans or fit mosquito nets over beds and baby carriers. Spraying sleeping areas with an effective insecticide may also help lower the risk.
Removing mosquito breeding sites around the home also reduces the risk. This means clearing stagnant water from pots, containers and other waste, disposing of rubbish properly and covering, emptying and cleaning water storage containers regularly
Communities can also help reduce mosquito breeding by eliminating standing water in public and private spaces wherever possible
Recognizing symptoms
Approximately 70–80% 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. Severe disease can cause high fever, neck stiffness, disorientation, tremors, convulsions, muscle weakness, paralysis or coma
If you experience any symptoms after returning from an area where West Nile virus is circulating, seek medical care promptly
Anyone who develops severe symptoms should seek urgent medical care. Treatment focuses on rest, fluids, pain relief and, in severe cases, hospital-based supportive care
West Nile virus infection can be confirmed through laboratory testing, including detection of virus-specific antibodies or viral RNA, depending on the stage of illness
