France, Aug. 19 -- The chikungunya cases are described as "autochthonous", meaning the virus was contracted in France rather than brought back by someone from abroad.

The largest-known outbreak of 16 cases is in Prignac-et-Marcamps, north of Bordeaux, where authorities have carried out insecticide treatments in parks and gardens.

They are also removing stagnant water where the invasive tiger mosquito lays its eggs.

France ramps up fight against tiger mosquitoes after record outbreaks Ideal conditions

The tiger mosquito, known scientifically as Aedes albopictus, is originally from Southeast Asia and can transmit chikungunya as well as dengue and Zika.

First detected in mainland France in 2004, it is now present across most of the coun...