Key Points

• From January 1 to May 31, 2025, 658 cases of measles were reported to regional health agencies (ARS), a total that already exceeds the number of cases reported in 2024 (483) by more than 35%. Nationally, the number of reported cases appears to have peaked in March but remains high, particularly in certain regions.

• The four age groups most affected, accounting for nearly half of the cases, were children aged 1–4 (15%), adolescents aged 15–19 (13%) and 10–14 (12%), and adults over 40 (12%). The highest rate of reported measles cases was observed among infants under 1 year of age (9.6 cases per 100,000).

• For 222 cases (33.7%), a visit to the emergency department or hospitalization was reported (including 10 in intensive care), and for 87 cases (13.2%), a complication was reported (including 50 cases of pneumonia and 1 case of encephalitis). Two deaths were reported among immunocompromised patients. Hospitalizations and complications primarily affected infants and young children as well as young adults.

• Among the target population for vaccination (aged over 1 year and born since 1980), for whom vaccination status was known (n=429 cases), 304 (70.8%) cases occurred in unvaccinated or incompletely vaccinated individuals.

• Sixty-three departments in mainland France reported at least one case, representing more than half of the departments (62.4%). No cases were reported in the overseas territories. More than half of the reported cases were concentrated in 9 departments: Nord (117 cases), Bouches-du-Rhône (50 cases), Isère and Haute-Savoie (39 cases each), Hérault (27 cases), Paris (25 cases), Seine-Saint-Denis (22 cases), Pas-de-Calais (22 cases), and Val-d’Oise (20 cases).

• During this period, 86 clusters (groups of epidemiologically linked cases) were reported to the ARS, totaling 370 cases. Among these, 18 clusters included 5 or more cases.

• Of the 658 reported cases, 94 (14%) were imported cases (defined as a stay abroad during the 7 to 18 days preceding the rash).

• Prompt reporting of cases to the ARS and the submission of biological samples to the National Measles Reference Center are essential for the early identification of clusters and the implementation of prevention and post-exposure prophylaxis measures around cases, particularly within communities.

• Strengthening catch-up vaccination efforts is crucial during this period. Any contact with a healthcare professional should be an opportunity to verify the vaccination status of individuals born since 1980. Vaccination with the MMR vaccine is indeed the best way to protect oneself from the virus, but also to protect vulnerable individuals at risk of severe disease (infants under one year of age, pregnant women, and immunocompromised individuals) who cannot be vaccinated.