Epidemiological Situation

The seasonal influenza epidemic in Mayotte began early this year (week 39 according to sentinel physicians). Indeed, for several years now, surveillance data have shown an increase in influenza-like illnesses during the rainy season, particularly from January to March. In 2016, this seasonal pattern was confirmed by the identification of influenza viruses at the CHM laboratory, as part of the virological surveillance program initiated that same year. In 2017, early activity was observed, showing a steady increase from week 39 to week 42. This trend will need to be confirmed in the coming weeks.Given the epidemic currently raging in Réunion and the travel between Mayotte and Réunion during this school vacation period, it is likely that influenza viruses were imported into Mayotte and are responsible for this resurgence.

By comparison, in Réunion, located in the Southern Hemisphere within the intertropical zone, influenza seasonality is marked by a surge in epidemiological surveillance indicators during the southern winter (see: PE Cire OI No. 52). In Mayotte, an island located in a zone closer to the equator, this seasonality is poorly understood. Several studies show that in tropical zones, flu epidemics occur during hot and humid periods, whereas in temperate zones, epidemics occur during cold and dry periods.

Furthermore, Mayotte maintains regular exchanges with mainland France, with daily flights between the two territories. This could contribute to the importation of influenza viruses from mainland France, which experiences the same peak season as Mayotte (mainland winter). To better understand the epidemiological dynamics of influenza in Mayotte, virological surveillance was established in 2016. It is conducted year-round through sentinel physicians and the CHM laboratory.