Animal disease detected West Nile virus reaches Switzerland
For the first time, a person in Ticino has been infected with West Nile virus without having been infected abroad. According to the health authorities, such a case was to be expected.
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- The first locally acquired case of West Nile virus confirmed in Switzerland has been identified in Ticino.
- The affected person has been hospitalized; there is no human-to-human transmission.
- The mosquito season is over, which is why the authorities say there is no immediate danger to the population.
The health authorities of the canton of Ticino, in collaboration with the federal government, have confirmed the first case of West Nile virus in Switzerland. According to the Department of Health and Social Affairs, this is a locally acquired infection - an event that had been expected in view of previous evidence of the virus in mosquitoes from the region.
The affected person, a patient living in Ticino, had shown symptoms in recent weeks and had to be hospitalized. Diagnostic tests finally confirmed the infection. This is the first known case of a person in Switzerland who has been infected domestically; previously the virus had only been detected in individual mosquitoes.
The virus was detected in mosquitoes in the summer
The West Nile virus is widespread in northern Italy and has been monitored in Ticino for years by the SUPSI and cantonal authorities. The pathogen was already found in local mosquitoes in random samples in the summer of 2025. The authorities emphasize that the current case confirms the effectiveness of the existing surveillance system.
However, there is no immediate risk to the population. The mosquito season is over and the virus cannot be passed on from person to person. In contrast to diseases such as dengue or chikungunya, humans are so-called false hosts and play no role in the transmission chain between mosquitoes and birds.
Most infections are mild or even asymptomatic; severe neurological complications are rare. The authorities have announced that they will continue to monitor the situation closely and inform the population again about precautionary measures before the start of the next mosquito season.
