Key Points

Chikungunya, Dengue, and Zika

• Since May 1, 2026, 106 imported cases of dengue, 31 imported cases of chikungunya, and 1 imported case of Zika have been identified and investigated in the Île-de-France region (compared to 203 imported cases of dengue and 182 imported cases of chikungunya during the same period in 2025).
• In the Île-de-France region, the first outbreak of locally transmitted chikungunya was identified in Nogent-sur-Marne in Val-de-Marne (94), with 6 cases identified to date. The onset dates of symptoms for these five cases range from August 16 to August 29.

West Nile Virus Infections

• As of September 20, 206, 20 locally transmitted human cases of West Nile virus (WNV) infection have been identified in Île-de-France.
• WNV was first detected in the region in May 2026 in mosquito excreta collected from a trap set up in department 94. Since June 2026, the National Reference Laboratory for West Nile Virus (ANSES) has detected 7 avian cases testing positive for WNV in 5 departments of Île-de-France (75, 77, 92, 94, and 95). Eight equine cases have been confirmed positive in departments 77, 91, 94, and 95.

COVID-19

• Emergency room visits: The number of emergency room visits for suspected COVID-19 continued to rise in Week 38 across all age groups. The numbers were approaching those observed in 2024 and 2025 during the same period.
• SOS Médecins: The number of consultations for suspected COVID-19 continued to rise in Week 38. This increase was particularly evident among children and adults under 65 years of age. The numbers were approaching those observed in 2025 during the same period and remained low compared to 2024.
• SARS-CoV-2 in wastewater: A strong upward trend in SARS-CoV-2 circulation in wastewater continued in Week 38 in the Île-de-France region. The level of circulation reached values last seen in October 2024. Increases in wastewater concentrations generally precede observed increases in human cases, without prejudging the magnitude of these increases or the clinical severity of the cases.