Key Points 

• In 2025, 95 cases of IIM were reported in the region (+5.5% compared to 2024), confirming the resurgence observed since late 2022.
• For the fourth consecutive year, the regional reporting rate exceeded that of the rest of mainland France (1.15 cases vs. 0.89 cases per 100,000 inhabitants).
• At the beginning of 2025, the number of IIM cases was exceptionally high, coinciding with a severe seasonal influenza epidemic in 2024/25.
• In 2025, serogroup B accounted for 44% of reported cases, serogroup W for 31%, and serogroup Y for 20%. The resurgence of IIM cases over the past three years involves serogroups B, W, and Y; however, the increase compared to pre-COVID years is greater for serogroups W and Y.
• In 2025, IIM reporting rates are higher among children under 5 years of age and adults aged 80 and older. The median age of cases (41 years) is increasing compared to 2024, which may be explained by the rise in the number of cases among people aged 60 and older, linked to the spread of serogroups W and Y.
• In 2025, the case fatality rate for IIM is 10%. Serogroup W is responsible for more than half of the deaths, highlighting the particular severity of infections associated with this serogroup.
• The rise in serogroups W and Y led to a revision of the vaccination schedule in 2025; the tetravalent ACWY vaccine is now mandatory for infants and children up to age 2, and recommended for adolescents aged 11 to 14, with catch-up vaccination available up to age 24.