Paris Fumigates for Tiger Mosquitoes for First Time as Tropical Disease Vectors Spread North

In the early hours of Thursday, roads were closed in southeast Paris and residents were asked to stay inside while pest control contractors moved through the streets spraying insecticide into trees, green spaces and other places where mosquitoes breed. It was the first time health authorities had fumigated any part of the French capital against tiger mosquitoes.

The trigger was a single case. The regional health body, ARS Ile-de-France, said the treated zone covered 150 metres around the home of a person in the 13th district who had caught dengue fever while travelling. The agency described the operation as a way to reduce the risk of dengue transmission once a case has been detected.

The logic is simple. A tiger mosquito, known scientifically as Aedes albopictus, becomes a carrier when it bites a person who has brought a virus home from abroad. From there it can pass the disease to others. Authorities are trying to stop that chain before it forms in the Paris region, which has an estimated 12 million people.

A second operation was planned for overnight Thursday into Friday in Colombes, a suburb northeast of central Paris, after another person fell ill with dengue following a trip overseas. In both cases the patients were infected abroad, and the spraying is aimed at preventing local spread.

Such scenes are routine in tropical cities and increasingly common in Europe. The tiger mosquito is native to southeast Asia and can carry dengue, chikungunya and Zika viruses. Anne Souyris, the deputy mayor of Paris in charge of health policy, told BFM television that the operation was a first for Paris but not for France, noting that the south of the country has dealt with tiger mosquitoes for some years.

The insect reached southern Europe in the first decade of this century and has moved north steadily since, establishing itself in France, Germany and Switzerland. It was first spotted in France in 2004. According to health ministry data, it is now present in 71 of the 96 departments on the French mainland, including areas near the northern Channel coast.

Health experts link that advance in part to climate change. Warmer weather shortens the incubation period of the mosquito's eggs, and winters are no longer cold enough to kill the insects off. Marie-Claire Paty, who heads a vector-borne disease monitoring unit at the public health body Sante Publique, told AFP in April that her team is convinced the risk will grow.

For now, the Paris operations are targeted responses to two imported dengue cases. What to watch is whether further cases prompt more fumigations, and whether any infection is ever traced to a mosquito bite within the region itself.