BELLINZONA. Four people in Ticino have had chikungunya without travelling to catch it, and they live in the same neighbourhood on the Piano di Magadino. The canton’s vector specialists, at the University of Applied Sciences and Arts of Southern Switzerland, call it the first known transmission of a virus by tiger mosquitoes in the canton. The cantonal doctor, Giorgio Merlani, says two of the four may have been bitten by the same insect. The others, he told Keystone-SDA, were most likely bitten by related mosquitoes.
The infections date from the end of the summer. No new local cases have been recorded since October. With the temperature down, tiger mosquitoes are fewer and less active. Merlani’s line, given to Ticino News, is that there is no cause for alarm, that cases of this kind were broadly expected, and that from now until next summer “it is no longer an issue”. The current risk, the canton says, is very low.
Why one street is the whole map
A tiger mosquito, Aedes albopictus, rarely flies much more than 100 metres in its life. That is why a cluster on a single street is both the warning and the limit. The insect that bites a person carrying the virus, and then bites a neighbour, does not tour the canton. It stays in the block. Working with SUPSI, the canton sprayed an adulticide into the air in the neighbourhood. Merlani said the spray is effective precisely because the mosquito’s world is so small.
The tiger mosquito has been established in Ticino for more than twenty years. What had not been recorded, until this cluster, was a chain of infection that began and ended locally: a mosquito already here bites someone who arrived infectious from a region where the virus circulates, and then passes it on. The four patients are described as autochthonous cases. They did not need a flight of their own to get sick. They needed a neighbour’s infection, and an insect that never left the street.
What the illness is, and what the canton is asking people to do
Chikungunya typically brings fever, joint pain and, in some patients, a rash. It is not a disease the canton is treating as an emergency this week. It is a disease Merlani wants doctors and patients to remember next summer, including when the patient has not travelled. Anyone coming back from an area where the virus circulates should tell a doctor about the trip if symptoms appear, and should keep avoiding bites after they return. That advice is about breaking the next chain, not about the four people already counted.
Residents of the Piano di Magadino do not need a new daily routine in November. The spray has been done. The season that supports the mosquito is over. What changes is the medical habit. A fever and joint pain in Lugano or Bellinzona in August can no longer be filed, automatically, under “probably not, they did not go anywhere”. Ticino has now seen the local route. The canton’s job over the winter is to keep the breeding sites down, so that a short-lived insect has fewer places to start.