An unusual increase in cases of invasive meningococcal infection between late 2022 and early 2023. These cases sometimes had atypical presentations (large numbers of bacteremias without meningitis). The distribution of serogroups was also unusual in our center (large number of serotype Y meningococcal IMD).

This development comes after three years marked by the Corona-Virus-Disease-19 pandemic, which led to a profound change in the behaviors involved in the transmission of infectious diseases. Barrier measures have considerably reduced the population's exposure to meningococcus, and may have encouraged a reduction in mucosal immunity to this pathogen. The end of 2022 was also marked by intense viral circulation (syncitial respiratory virus-influenza-COVID), which may have favored invasive forms.

Invasive meningococcal disease (IMD) accounts for a small number of cases (500-600 cases/year) in mainland France. Despite advances in its management, the disease is still associated with a 10-20% mortality rate and impaired quality of life in 50% of surviving patients.

An unusual increase in cases of invasive meningococcal infection during the winter of 2022. These cases often had atypical presentations (large number of bacteremias without meningitis, digestive picture in the foreground). The distribution of serogroups was also unusual at our center (large number of serotype Y meningococcal IMD). These data appear to be confirmed by Santé Publique France's national data for 2022, with no warning of the spread of a hyper-virulent clone.

This development comes after three years marked by the SARS-CoV2 pandemic, which led to a profound change in the behaviors involved in the transmission of infectious diseases .

Barrier measures have considerably reduced the population's exposure to meningococcus, and may have led to a reduction in mucosal immunity to this pathogen. This is particularly true of teenagers and young adults, for whom contact has fallen sharply due to the closure of schools and universities. It would be interesting to see whether this population is more affected this year than in previous years.

The end of 2022 was also marked by intense viral circulation (SRV-Flu-Covid), which could have favored invasive forms. Evidence of a significant number of viral co-infections could support this hypothesis.

Inclusion Criteria:

Clinical diagnosis of Invasive Meningococcal infection (defined by the isolation of Neisseria meningitis in a normaly steril site (CSL, blood, articulation, ..) by PCR or culture.

No exclusion Criteria

Patient from the West part of France