France has recorded nearly 400 locally-acquired cases of chikungunya this summer, a sharp increase from last year, French health authorities announced today.

As of Sept. 8, there have been 382 cases of chikungunya from infected mosquitoes biting people in mainland France, including 81 from the past week alone, in addition to 966 imported cases. The country also reported 21 cases of locally-acquired dengue and 894 imported cases.

It’s a stark increase in the number of chikungunya cases from mosquitoes in the country compared to last year, when only one such case was reported in France.

Chikungunya can cause flu-like symptoms, such as high fever, headache, nausea, rash, and muscle and joint pain. Most people recover, although 30 to 40 percent of those affected develop chronic arthritis.

Tiger mosquitoes are increasingly spreading across Europe as climate change makes environmental conditions more habitable, raising the risk that vector-borne diseases once limited to the tropics become endemic across the continent.