Cases of the potentially deadly virus have been reported in Spain and Italy.
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A dengue fever outbreak in Europe in the spring prompted travellers to be on alert, but now cases of another potentially deadly mosquito-borne virus have been reported.
West Nile virus has been detected in two people in Spain and Italy, and the European Centre for Disease Prevention and Control (ECDC) says the infection was acquired locally and not during travel to tropical regions.
The Italian case was discovered on June 20 in Modena, a city in the northern Emilia-Romagna region, following a case identified in Seville, Spain, in March.
What is West Nile Virus and what are the symptoms?
West Nile virus (WNV) is a potentially fatal neurological disease in humans and belongs to the Japanese encephalitis virus group, which includes dengue fever and yellow fever.
Birds are the natural host for WNV, but it is usually spread by mosquitoes and, in a few cases, through blood transfusions, organ donation, and pregnancy.
About four in five people with West Nile virus never develop symptoms, but the remaining 20 percent develop symptoms of West Nile virus, including sudden onset of high fever, headache, stiff neck, a rash on the neck, arms and legs, and in more severe cases, seizures, muscle weakness and paralysis, according to the ECDC.
People over 50 years of age, especially those with underlying medical conditions, are more likely to become seriously ill. Fewer than 1% of people develop neurological infections such as meningitis or encephalitis, and of those, one in 10 die.
Symptoms usually appear 2-6 days after infection, but may take 14 days or more to develop. If there are no complications, symptoms usually subside within 3-6 days.
How to protect yourself from West Nile virus
There is no WNV vaccine for humans yet, so the best way to protect yourself is to avoid mosquito bites.
To achieve this, people should avoid traveling to infected areas during times when mosquitoes are more prevalent, such as in the summer, and reduce the amount of time they spend outdoors when they are in infected areas.
The virus was first detected in the West Nile region of Uganda in 1937, but is now found in countries around the world, including Africa, the Middle East, Western and Central Asia, North America, and Southern and Eastern Europe.
Using mosquito repellent, covering the arms, legs, and feet, and preventing mosquitoes from entering the bedroom at night can also help prevent infection.
If you feel unwell, especially if you have a fever, contact your doctor and tell them where you have traveled recently.
Why are there more cases of mosquito-borne diseases in Europe?
Record heat and other extreme weather caused by climate change are causing a surge in virus infections in Europe.
“We already see in Europe that climate change is allowing non-native mosquito species to spread to previously unaffected areas, creating favourable conditions for transmitting diseases such as dengue fever,” ECDC director Andrea Amon said last month.
“Increased international travel from dengue-endemic countries will also increase the risk of imported infection and, inevitably, the risk of local outbreaks,” she added.
Locally transmitted cases of dengue in Europe are set to nearly double between 2022 and 2023, with figures suggesting it could become even more prevalent this year.
Where in Europe is infection most likely to occur?
The dengue-transmitting Asian tiger mosquito is currently established in 13 European countries: Austria, Bulgaria, Croatia, France, Germany, Greece, Hungary, Italy, Malta, Portugal, Romania, Slovenia and Spain.
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The first large-scale WNV outbreak in Europe occurred in Romania in 1996. Since then, cases have been confirmed in other European countries, including France, Greece, Hungary, Italy, Portugal, and Spain.
In 2023, 713 cases of autochthonous transmission were reported in 123 EU/EEA territories, of which 22 territories confirmed cases for the first time. Sadly, 67 deaths were reported.
Cases confirmed in Spain in March this year occurred unusually quickly, likely due to unseasonably warm weather.
The ECDC warns that mosquitoes that carry dengue and Zika viruses are spreading further north, east and west in Europe, and have recently become established in Cyprus.
