Key Points 

Chikungunya, Dengue, and Zika

• Since May 1, 2026, 73 imported cases of dengue, 14 imported cases of chikungunya, and 2 imported cases of Zika have been identified and investigated in Île-de-France (compared to 144 imported cases of dengue and 156 imported cases of chikungunya during the same period in 2025). There has been no local transmission in Île-de-France in 2026, as of now.

West Nile Virus Infections

• The National Reference Laboratory for West Nile Virus detected 6 avian cases positive for WNV in June 2026 across 4 departments in the Île-de-France region (75, 77, 92, and 94). The West Nile virus had been identified in mosquito excreta collected from a trap set up in department 94 in May 2026. No human or equine cases have been detected in the region in 2026, as of now.

Smallpox B (Mpox)

• As of August 9, there were 125 confirmed cases in Île-de-France for 2026 (Figure 2), a higher total than in 2025 (115 cases in total in 2025). 

• In April 2026, the number of smallpox B cases in Île-de-France peaked at 36, four times the number recorded in March 2026, when 9 cases were reported. A gradual decline was then observed in May and June, before the number stabilized in July at around 20 cases per month. 

Asthma

• The summer vacation period corresponds to the time when the risk of asthma exacerbations is lowest. Maintenance treatment for asthma patients is sometimes paused during the summer at the initiative of the doctor or the family, with parents instructed to resume it before school starts. It is important to resume maintenance treatment at least 8 days before school starts to ensure an asthma-free start to the school year.

Dermatophilus congolensis

• This is a bacterium that typically causes skin infections in horses and cattle. Several regions in France reported human cases in 2026, primarily among men who have sex with men. The majority of cases had visited a sauna where sexual contact occurred before the onset of symptoms. Transmission is facilitated by warm, humid environments.