Summary

Since 2004, when it was first identified in the Alpes-Maritimes department, the “tiger” mosquito Aedes albopictus—a vector capable of transmitting the dengue, chikungunya, and Zika viruses—has gradually expanded its geographic range in mainland France. Present in Île-de-France since 2015, Aedes albopictus is considered to be established and active in municipalities across all departments in the region.

An integrated surveillance system was established in 2006 to combat the risk of arboviral diseases in metropolitan France. It relies on epidemiological surveillance based primarily on the mandatory reporting (DO) system for biologically confirmed cases. Surveillance is intensified from May 1 to November 30 during the mosquito’s active season through the tracking of unreported cases identified using data from medical testing laboratories. The identification and investigation of all identified cases help guide vector control (LAV) actions implemented by mosquito control operators.

This bulletin provides an epidemiological and entomological summary of the enhanced surveillance seasons (May 1 to November 30) for the years 2022 and 2023 in Île-de-France.

Key Points

• During the 2022 season, 91 confirmed or probable cases were reported, all of which were imported: 80 cases of dengue, 10 cases of chikungunya, and 1 case of Zika.

• During the 2023 season, 704 confirmed or probable cases were reported: 691 cases of dengue, 6 cases of chikungunya, 6 cases of Zika, and one case of dengue-chikungunya co-infection; this sharp increase was linked to the major dengue epidemic in the French West Indies.

• In 2023, the first outbreak of indigenous vector-borne transmission was identified in Île-de-France.

• By the end of 2022, 106 areas (100 municipalities and 6 Parisian arrondissements) had been identified as colonized by Aedes albopictus. The proportion of the regional population living in colonized areas was 39%.

• By the end of 2023, 175 areas (161 municipalities and 14 Parisian arrondissements) had been identified as colonized. The proportion of the regional population living in colonized areas rose to 61%.