They said it had not yet been determined whether the tiger mosquitoes found so far are isolated individuals or part of an established local colony.
Aedes albopictus can also carry the chikungunya virus, which infected more than 160 people in northern Italy earlier this year. In Switzerland, it had only been found previously south of the Alps, in the canton of Ticino.
The Swiss health ministry plans to make chikungunya, which was described for the first time in Tanzania in 1952, a mandatory reportable disease from next year.
The mosquito is also present in southern France and parts of Spain, as well as the United States, but the outbreak of chikungunya in Italy is thought to have been the first outside the tropics.
Chikungunya gets its name from a Swahili word meaning "that which bends up" because of the arthritic-type symptoms that leave victims stooped.
Also causing fever, headaches and muscle pain, it has traditionally been present in eastern Africa, southeast Asia and the Indian subcontinent. Most patients eventually recover.
Dengue fever, another disease of tropical origin, is a flu-like illness which is especially dangerous in children and the elderly, who have little resistance and often die of internal bleeding.
Health experts meeting in Stockholm in September said European countries must work to control tiger mosquito populations, but the situation was not alarming.