Résumé
Context In low-income settings where access to biological diagnosis is limited, data on the spread of the COVID-19 epidemic are scarce. In September 2020, after the first COVID-19 wave, Mali reported 3,086 confirmed cases and 130 deaths. Most reports originated form Bamako, the capital city, with 1,532 reported cases and 81 deaths for an estimated 2.42 million population. This observed prevalence of 0.06% appeared very low. Our objective was to estimate SARS-CoV-2 infection among inhabitants of Bamako, after the first epidemic wave. We also assessed demographic, social and living conditions, health behaviors and knowledge associated with SARS-CoV-2 seropositivity. Material and methods We conducted a cross-sectional multistage cluster household survey in commune VI, which reported, at this time, 30% (n=466) of the total cases reported at Bamako. We measured serological status by detection of SARS-CoV-2 spike protein Antibodies in venous blood sampled after informed consent. We documented housing conditions and individual health behaviors through KABP questionnaires among participants aged 12 years and older. We estimated the number of SARS-CoV-2 infections and deaths in the total population of Bamako using the age and sex distributions of SARS-CoV-2 seroprevalence. A logistic generalized additive multilevel model was performed to estimate household conditions and demographic factors associated with seropositivity. Results We recruited 1,526 inhabitants in the 3 investigated areas (commune VI, Bamako) belonging to the 306 sampled households. We obtained 1,327 serological results, 220 household questionnaires and collected KABP answers for 962 participants. The prevalence of SARS-CoV-2 seropositivity was 16.4% after adjusting on the population structure. This suggested that ~400,000 cases and ~ 2,000 deaths could have occurred of which only 0.4% of cases and 5% of deaths were officially reported. KABP analyses suggested strong agreement with washing hands but lower acceptability of movement restrictions (lockdown or curfew), and limited mask wearing. Conclusion In spite of limited numbers of reported cases, the first wave of SARS-CoV-2 spread broadly in Bamako. Expected fatalities remained limited largely due to the population age structure and the low prevalence of comorbidities. This highlight the difficulty of developing epidemic control strategies when screening test are not available or not used, even more when the transmission modalities are not well known by the population. Targeted policies based on health education prevention have to be implemented to improve the COVID-19 risk perception among the local population and fight to false knowledge and beliefs.
Sujets)
COVID-19 , Syndrome respiratoire aigu sévèreRésumé
Investment in Africa over the past year with regards to SARS-CoV-2 genotyping has led to a massive increase in the number of sequences, exceeding 100,000 genomes generated to track the pandemic on the continent. Our results show an increase in the number of African countries able to sequence within their own borders, coupled with a decrease in sequencing turnaround time. Findings from this genomic surveillance underscores the heterogeneous nature of the pandemic but we observe repeated dissemination of SARS-CoV-2 variants within the continent. Sustained investment for genomic surveillance in Africa is needed as the virus continues to evolve, particularly in the low vaccination landscape. These investments are very crucial for preparedness and response for future pathogen outbreaks.
Résumé
The progression of the SARS-CoV-2 pandemic in Africa has so far been heterogeneous and the full impact is not yet well understood. Here, we describe the genomic epidemiology using a dataset of 8746 genomes from 33 African countries and two overseas territories. We show that the epidemics in most countries were initiated by importations, predominantly from Europe, which diminished following the early introduction of international travel restrictions. As the pandemic progressed, ongoing transmission in many countries and increasing mobility led to the emergence and spread within the continent of many variants of concern and interest, such as B.1.351, B.1.525, A.23.1 and C.1.1. Although distorted by low sampling numbers and blind-spots, the findings highlight that Africa must not be left behind in the global pandemic response, otherwise it could become a breeding ground for new variants.
Résumé
We are currently facing a pandemic of COVID-19, caused by a spillover from an animal-originating coronavirus to humans occuring in the Wuhan region, China, in December 2019. From China the virus has spread to 188 countries and regions worldwide, reaching the Sahel region on the 2nd of March 2020. Since whole genome sequencing (WGS) data is very crucial to understand the spreading dynamics of the ongoing pandemic, but only limited sequence data is available from the Sahel region to date, we have focused our efforts on generating the first Malian sequencing data available. Screening of 217 Malian patient samples for the presence of SARS-CoV-2 resulted in 38 positive isolates from which 21 whole genome sequences were generated. Our analysis shows that both, the early A (19B) and the fast evolving B (20A/C) clade, are present in Mali indicating multiple and independent introductions of the SARS-CoV-2 to the Sahel region.