Key Points

Heat Waves, Extreme Heat

• A regional analysis of emergency department visits shows stable trends in the number of visits for all causes and in the proportion of hospitalizations following emergency department visits for the composite health indicator iCanicule (which includes hyperthermia, dehydration, and hyponatremia). There was also a decrease in emergency department visits for the composite health indicator iCanicule and in hospitalizations following emergency department visits for all causes.
• A regional analysis of SOS Médecins calls also shows that the composite health indicator iCanicule (heatstroke, dehydration) remained stable throughout the entire heatwave. There was an increase in SOS Médecins calls (no data for Val-d’Oise) for all causes during the same period.
• This trend falls within the expected range of fluctuations given the current weather conditions and is observable across the region as a whole. 

Chikungunya, Dengue, and Zika

• Since May 1, 2026, 75 imported cases of dengue, 15 imported cases of chikungunya, and 2 imported cases of Zika have been identified and investigated in Île-de-France (compared to 153 imported cases of dengue and 161 imported cases of chikungunya during the same period in 2025). No local transmission has been detected in Île-de-France in 2026, as of this writing.

West Nile Virus Infections

• As of August 17, 206, three locally acquired human cases of West Nile virus (WNV) infection were identified in Île-de-France: two cases in Essonne (91) and one case in Seine-Saint-Denis (93).
• WNV was first detected in the region in May 2026 in mosquito excreta collected from a trap set up in department 94. In June 2026, the National Reference Laboratory for West Nile Virus (ANSES) detected 6 avian cases positive for WNV in 4 departments of Île-de-France (75, 77, 92, and 94).