ASSESSING THE EXTENT OF COVID-19 TRANSMISSION IN FRENCH GUIANA

The emergence of SARS-CoV-2 was accompanied by great uncertainty regarding the main epidemiological characteristics of the transmission. In a context where epidemiological surveillance was mainly targeted on symptomatic patients, we assessed the extent of SARS-CoV-2 transmission in French Guiana conducting an intra-household transmission study and population-based seroprevalence surveys repeated over time. Household monitoring included virological and clinical follow-up for all household members for the first 28 days after the date of confirmation of the index case and serological follow-up over a 12-month period. Three seroprevalence surveys were conducted in July and September 2020 and in September 2021. A total of 57 dwellings including 245 individuals were included in the intra-household study. The average time between the date of onset of symptoms and the date of confirmation of diagnosis and inclusion in the study was 4.2 days and 7.2 days respectively. Secondary transmission was found in three quarters of households with a secondary infection rate of 35%. The highest transmission rate were observed in the most disadvantaged populations, within couples and from adults to children. Population-based seroprevalence studies have made it possible to monitor seroprevalence rates, which have varied from 15% at the time of the epidemic peak of the first epidemic wave to 65% of the population at the beginning of the fourth wave, despite the low impact of vaccination in French Guiana. The results obtained highlighted a high transmission of the virus in French Guiana associated with a low severity rate linked to the structure of the particularly young population. The project has provided health authorities with useful data to support prevention and control strategies and has allowed to evaluate the impact of interventions implemented during the pandemic.