Swiss canton finds no sign of tropical viruses in mosquitoes
No tropical viruses have been detected in the mosquito population in the Swiss canton of Basel-City.
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The cantonal laboratory has found no trace of dengue, chikungunya, Zika or West Nile viruses in an investigation, it announced on Wednesday.
The risk of local transmission of these pathogens by the tiger mosquito can therefore still be considered low. Only the Usutu virus, which is transmitted by the native mosquito species and mainly infects birds, has been detected.
The cantonal laboratory analysed 5,674 mosquitoes last year. It collected mosquitoes with traps at ten locations in Basel, Riehen and Allschwil every week between August and November. Of the insects caught, native Culex mosquitoes made up the vast majority (97.6%).
These can also transmit diseases, mainly the West Nile and Usutu viruses. In 2022, Culex mosquitoes with West Nile virus were detected in Ticino for the first time. Usutu virus, on the other hand, usually causes no symptoms or only mild symptoms in humans when infected.
Monitoring continues
The remaining 2.4% of the insects belonged to the genus Aedes, which includes the Asian tiger mosquito.
Using a method established by the laboratory, it is now possible to assess the spread of these viruses in the local mosquito population. Monitoring will continue at six locations this year.
According to the EU Centre for Disease Prevention and Control, several cases of chikungunya were reported in France this summer. Near Strasbourg, only around 130 kilometres from Basel, a person was infected with the chikungunya virus for the first time.
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Translated from German by DeepL/mga
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