Epidemiological profile of COVID-19 in the French overseas department Mayotte, 2020 to 2021

Background: During the COVID-19 pandemic, national and local measures were implemented on the island of Mayotte, a French overseas department in the Indian Ocean with critical socioeconomic and health indica-tors. Aim: We aimed to describe the COVID-19 outbreak in Mayotte from March 2020 to March 2021, with two waves from 9 March to 31 December 2020 and from 1 January to 14 March 2021, linked to Beta (20H/501Y. V2) variant. Methods: To understand and assess the dynamic and the severity of the COVID-19 outbreak in Mayotte, surveillance and investigation/contact trac-ing systems were set up including virological, epide-miological, hospitalisation and mortality indicators. Results: In total, 18,131 cases were laboratory con-firmed, with PCR or RAT. During the first wave, inci-dence rate (IR) peaked in week 19 2020 (133/100,000). New hospitalisations peaked in week 20 (54 patients, including seven to ICU). Testing rate increased tenfold during the second wave. Between mid-December 2020 and mid-January 2021, IR doubled (851/100,000 in week 5 2021) and positivity rate tripled (28% in week 6 2021). SARS-CoV-2 Beta variant (Pangolin B.1.351) was detected in more than 80% of positive samples. Hospital admissions peaked in week 6 2021 with 225 patients, including 30 to ICU. Conclusion: This massive second wave could be linked to the high transmissibil-ity of the Beta variant. The increase in the number of cases has naturally led to a higher number of severe cases and an overburdening of the hospital. This study shows the value of a real-time epidemiological surveil-lance for better understanding crisis situations.