After more than two years of low incidence during the COVID-19 pandemic, an upsurge in invasive meningococcal infections (IMIs) has been observed in the 2022/23 season, Santé publique France reports.
A peak in incidence was observed in December 2022, particularly during week 52/2022. This peak was early compared to the seasonal peak observed during the pre-pandemic seasons (peak between January and March depending on the season). During the first quarter of 2023, the number of IMI cases remained at a high level (especially in January and March) compared to the incidence observed in the same months during the pre-pandemic seasons.
The rebound of IMI is not an unexpected phenomenon after two years of low meningococcal circulation. Two hypotheses can be put forward to explain this marked resurgence of IMIs:
- A higher risk of infection resulting from reduced immunity in the population having been less exposed to meningococci between 2020 and 2022 (barrier gestures, distancing);
- A more marked season in connection with the scale of the epidemics of seasonal viral infections in 2022/23, in particular infections by the influenza virus, which can lead to a risk of invasive bacterial infection (meningococci, streptococci).
The situation is very contrasted on the territory according to the serogroups. Spatio-temporal groupings of IMI B have been identified in 2022 (Auvergne Rhône Alpes, Strasbourg) and local vaccination campaigns have been implemented among the population. These situations seem to be contained to date, but they are still being carefully monitored. These phenomena can occur randomly in connection with the emergence and local implantation of certain strains of meningococci, which requires very regular monitoring of epidemiological data.
The rebound observed in the 2022-2023 season is a reminder of the importance of vaccinating infants to protect them against infections linked to serogroups B and C (recommendations recalled on the Vaccination Info Service website).
Public Health France is continuing to monitor IMIs in conjunction with its partners (ARS, CNR). This reactive surveillance allows the early detection of clusters of cases or unusual situations that can lead to the implementation of local vaccination campaigns in the event of a localized over-incidence.
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