Italy alone has reported 748 human cases of West Nile virus this season, and the figure for the whole of the European Union is far larger: 1,715 locally acquired infections as of Oct. 7, the highest number ever reported. Another 130 people have died, according to the European Centre for Disease Prevention and Control, which published the tally on Oct. 15.
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The count covers infections picked up inside the bloc’s own borders, not cases brought home by travelers. The agency says the virus is moving into new parts of Europe and expects that trend to continue in coming years, a pattern that puts a mosquito-borne disease once associated with the Mediterranean into countries far to the north. Health officials in affected regions have spent the autumn tracking cases week by week, and the October figure is the most complete picture so far of how large the season turned out to be.
A record built in the south and extended north
The ECDC news release as distributed through EurekAlert lists Italy as the hardest-hit country, with 748 cases. Greece and France each recorded their highest number of human cases ever. Those three southern and western countries drive the total, yet the notable detail for public health officials sits further north, where the virus has been turning up in places that rarely had to think about it. Reports of infections in birds and mosquitoes often precede human cases, which is one reason surveillance in animals matters as much as counting patients in hospitals.
The Netherlands has reported 59 human cases so far this year, and detections in both people and animals show the virus circulating there. Belgium has reported 15 human cases, and these are the first locally acquired human West Nile infections recorded in that country. The original ECDC announcement describes both as evidence that the virus is circulating further north than before.
Severity is not rising, even as the count climbs
A record case count invites the assumption that the disease itself has become more dangerous, and the agency says the data do not support that. ECDC sees no sign of increased severity this year. The shares of cases that were hospitalised, that developed neurological symptoms or that ended in death all remain below the levels seen over the past decade. More people are being infected, in other words, but a smaller proportion of them are becoming seriously ill. That distinction matters for hospitals and for travelers, because the likelihood of a severe outcome for any one infected person has not gone up even as the number of exposures has.
The World Health Organization’s fact sheet on West Nile virus explains why the proportions look that way. About 80 percent of infected people have no symptoms, roughly 20 percent develop West Nile fever with flu-like signs, and about one in 150 develops severe neurological disease. People over 50 and those with weakened immune systems face the highest risk, and no human vaccine exists.
Culex mosquitoes, especially Culex pipiens, are the main carriers, according to the same WHO page. The virus cycles between birds and mosquitoes, while people and horses are dead-end hosts that catch it from a bite but do not pass it on in that way. The long link between birds and mosquitoes is also why the virus can persist in a region year after year once it arrives, and why control efforts focus on mosquito populations and breeding sites rather than on patients.
ECDC expects more cases before the season ends
Conditions for transmission are becoming less favourable as summer ends, the agency says, but the virus may keep circulating at a lower level and more cases are expected. The tally is therefore a running figure rather than a final one. ECDC publishes a weekly seasonal surveillance report during the transmission season and a monthly report covering humans and animals, which is where later counts will appear. Because reporting lags behind infection, the final total for the season will probably be higher than the 1,715 recorded as of Oct. 7, and the deaths figure of 130 could rise as well.
Ole Heuer, Head of Unit at ECDC, said “The occurrence of West Nile virus varies considerably from year to year and is difficult to predict.” That caution cuts both ways: a record year does not guarantee another, but it also gives no basis for assuming the northward spread will reverse.
Céline Gossner, a senior expert at ECDC, called West Nile virus a clear example of why a cross-sector approach is essential, and she stressed that no single sector can address the risk alone. The agency’s recommendations for authorities follow that logic: combine mosquito monitoring, reduction of breeding sites and targeted control, and have public health, veterinary and environmental bodies work together under a One Health approach.
For individuals, the advice is practical and unchanged. Use mosquito repellent, wear loose long clothing in the evening and at night, and rely on window screens, mosquito nets or air conditioning where appropriate. Older adults and people with weakened immune systems are the groups ECDC singles out as most at risk of severe illness.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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