Headlines - Invasive meningococcal infections (IMI) in 2016

In 2016, 526 IIM cases were reported in France. The incidence rate, adjusted for underreporting, was estimated at 0.89 per 100,000 inhabitants in metropolitan France. Following an overall decline in the incidence rate between 2004 and 2014, an increase has been observed since 2015. This increase affected all serogroups. In 2016, serogroup B was the most common (51.6%), followed by serogroup C (26.5%), serogroup Y (12.3%), and serogroup W (8.9%). The case fatality rate was 12% for all cases of IIM.

The year 2016 was marked by an increase in the number of W IIM cases, particularly among adults (45 cases in 2016, representing 9% of IIM cases with a known serogroup). The strain responsible is an emerging strain genetically linked to strains that circulated in South America in the 2000s and in the United Kingdom since 2009. Its rapid spread in France over the past two years is a cause for concern.

It is associated with a high case-fatality rate in France (24% in 2016). Atypical forms have been described in France and other countries (initial gastrointestinal symptoms, arthritis, pneumonia, epiglottitis, etc.), which can lead to delayed diagnosis. In 2016, this hypervirulent strain caused a cluster of 3 cases among university students in Dijon, leading to a vaccination campaign targeting students and staff on the university campus (more than 13,000 people vaccinated).

The situation regarding IIM W continues to be closely monitored to identify any spatio-temporal clusters of cases early on and to contribute to any necessary adjustments to vaccination recommendations.