France and Italy Chikungunya Outbreaks Related to Tempurature

The French health ministry today published an updated Bulletin summarizing the unusually high number of chikungunya virus cases this year.

As of November 20, 2025, there have been 87 locally acquired cases of chikungunya in France: 43 in the Gard and 44 in the Hérault, located along France's Mediterranean coast.

Additionally, France confirmed 1,052 imported cases, with about 72% related to travelers from the department of La Réunion, located in the southwest Indian Ocean.

Seperately, Italy has reported 384 local cases, with the largest cluster located in Carpi, San Prospero, Soliera, Novellara, Cavezzo, Modena, Nonantola, Correggio, Novi di Modena, and Cesenatico.

The reasons behind these outbreaks may be weather-related.

On November 17, 2025, the European CDC reported that, according to data in the scientific literature, the ambient temperature is one of the most important environmental factors influencing the mosquito-borne transmission of the chikungunya virus.

The optimal daily average temperature for chikungunya transmission by Ae. albopictus in temperate zones of the Northern Hemisphere is 24–26 °C.

However, transmission might occur within the temperature range of 12 – 30 °C.

Currently, the U.S. CDC advises travelers to these areas to speak with a healthcare provider about chikungunya vaccination options.