In 2023, France recorded a sharp increase of 72% in cases of invasive meningococcal infections.
- After several years of low incidence, the 2022-2023 season showed an early and very high peak of IIM cases.
- In 2023, 560 cases of invasive meningococcal infections were recorded. This represents an increase of 72% in one year.
- Those under 5 years of age remained most at risk of B-MI. W-MI affected both babies and adults while Y-MI was more common in the elderly, but also affected adults and young people.
The number of cases of invasive meningococcal infections exploded in winter 2023 to reach “levels never before observed“, according to report from Public Health France, published on April 9, 2024.
Invasive meningococcal infections: an increase in cases of 72% in 2023
Invasive meningococcal infections (IMI), linked to bacteria called meningococci, cause life-threatening meningitis or septicemia. If the incidence was low for several years in particular because of the Covid-19 epidemic, the 2022-2023 winter season was marked by an early and very high peak in cases, including 89 cases in December 2022 and 80 cases in January 2023.
According to the annual report, 560 cases of invasive meningococcal infections were declared in 2023. This represents an increase of 72% compared to 2022. In detail, 44% of infections were linked to serogroup B, 29% to serogroup W and 24% to serogroup Y.
“IIM W were associated with high case fatality (19% with 31 deaths) compared to other serogroups (7% for IIM B and 8% for IIM Y)”specifies the report.
Meningococci: different developments depending on the type
Health professionals have observed contrasting developments depending on the types of meningococcal infections. If IIM C have become rare, cases linked to serogroup B, Y or W recorded significant increases in 2023.
“For serogroups B/W/Y, the number of cases of invasive meningococcal infections increased sharply among adults aged 25 and over, while the rebound in 2022 was initially observed among young adults aged 15- 24 years old. The increase in 2023 was particularly marked among people aged 60 and over.
For children under 5 years old, IIM B remained in the majority, representing almost 6 out of 10 cases. However, a slight decrease was observed compared to 2022 (67%). For their part, IIM Y and W represented a growing share of cases with 41% of cases among those under 5 years old (vs. 30% in 2022).
“This post-Covid-19 resurgence could be explained by the decline in immunity in the population less exposed to meningococci during the pandemic, but also by the return of respiratory viruses (in particular influenza) which can promote invasive bacterial infections Furthermore, the different evolution according to age could reflect a reintroduction of meningococci having first affected young adults in whom carriage is more frequent, followed by transmission to older age groups.
