Key Points

• A total of 326 confirmed cases of chikungunya were recorded between S10 and S20-2025.

• Chikungunya is circulating across nearly the entire territory of Mayotte, with a higher concentration in the municipalities of Mamoudzou, Pamandzi, Dzaoudzi, and Koungou.

• Surveillance systems need to be strengthened to better estimate the true extent of chikungunya circulation.

• Transition to Phase 2B of the ORSEC plan due to the intensification of the circulation of locally acquired chikungunya cases: several management and surveillance measures will be implemented to curb this trend and better prepare for a potential epidemic phase.

• A possible underestimation due to the lack of systematic use of biological confirmation tests for chikungunya in emergency departments and primary care, as well as limited access to care among part of the population.

• A slight increase in dengue circulation on the island, with 19 confirmed cases since the beginning of the year, including 10 between Week 19 and Week 20.