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. 2022 Mar 23;74(6):1030-1038.
doi: 10.1093/cid/ciab589.

Rapidly Increasing Severe Acute Respiratory Syndrome Coronavirus 2 Seroprevalence and Limited Clinical Disease in 3 Malian Communities: A Prospective Cohort Study

Issaka Sagara  1 , John Woodford  2 , Mamady Kone  1 , Mahamadoun Hamady Assadou  1 , Abdoulaye Katile  1 , Oumar Attaher  1 , Amatigue Zeguime  1 , M'Bouye Doucoure  1 , Emily Higbee  2 , Jacquelyn Lane  2 , Rathy Mohan  2 , Justin Doritchamou  2 , Irfan Zaidi  2 , Dominic Esposito  3 , Jennifer Kwan  4 , Kaitlyn Sadtler  5 , Alassane Dicko  1 , Patrick E Duffy  2
Affiliations

Rapidly Increasing Severe Acute Respiratory Syndrome Coronavirus 2 Seroprevalence and Limited Clinical Disease in 3 Malian Communities: A Prospective Cohort Study

Issaka Sagara et al. Clin Infect Dis. .

Abstract

Background: The extent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure and transmission in Mali and the surrounding region is not well understood. We aimed to estimate the cumulative incidence of SARS-CoV-2 in 3 communities and understand factors associated with infection.

Methods: Between July 2020 and January 2021, we collected blood samples and demographic, social, medical, and self-reported symptoms information from residents aged 6 months and older over 2 study visits. SARS-CoV-2 antibodies were measured using a highly specific 2-antigen enzyme-linked immunosorbent assay optimized for use in Mali. We calculated cumulative adjusted seroprevalence for each community and evaluated factors associated with serostatus at each visit by univariate and multivariate analysis.

Results: Overall, 94.8% (2533/2672) of participants completed both study visits. A total of 31.3% (837/2672) were aged <10 years, 27.6% (737/2672) were aged 10-17 years, and 41.1% (1098/2572) were aged ≥18 years. The cumulative SARS-CoV-2 exposure rate was 58.5% (95% confidence interval, 47.5-69.4). This varied between sites and was 73.4% in the urban community of Sotuba, 53.2% in the rural town of Bancoumana, and 37.1% in the rural village of Donéguébougou. Study site and increased age were associated with serostatus at both study visits. There was minimal difference in reported symptoms based on serostatus.

Conclusions: The true extent of SARS-CoV-2 exposure in Mali is greater than previously reported and may now approach hypothetical "herd immunity" in urban areas. The epidemiology of the pandemic in the region may be primarily subclinical and within background illness rates.

Keywords: COVID-19; Mali; SARS-CoV-2; West Africa; seroprevalence.

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Figures

Figure 1.
Figure 1.
Study flow chart. Visit 1 was completed between 29 July and 16 October 2020 at the Sotuba site, 29 July and 24 September 2020 at the Bancoumana site, and 28 July and 27 August 2020 at the Donéguébougou site. Visit 2 was completed between 21 December 2020 and 26 January 2021 at the Sotuba site, 28 December 2020 and 29 January 2021 at the Bancoumana site, and 14 December 2020 and 15 January 2020 at the Donéguébougou site. A total of 94.7% (2532/2672) of participants completed visit 2.
Figure 2.
Figure 2.
Seroprevalence of SARS-CoV-2 antibodies in Mali. Seroprevalence adjusted for population age distribution and assay sensitivity and specificity [15]. Error bars represent 95% confidence intervals. Asterisk represents P < .0001 in comparison between sites. SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
Figure 3.
Figure 3.
Longitudinal SARS-CoV-2 antibody reactivity spike protein and RBD at study sites: Sotuba (top row), Bancoumana (middle row), and Donéguébougou (bottom row). Visit 1: 28 July–16 October 2020. Visit 2: 14 December 2020–29 January 2021. OD, optical density; RBD, receptor binding domain; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
Figure 4.
Figure 4.
Odds ratio and 95% confidence intervals for covariates associated with serostatus at (A) visit 1 and (B) visit 2. Odds ratios following multiple logistic regression. Covariates with 95% confidence intervals crossing 1 in gray, not crossing 1 in black. Visit 1: 28 July–16 October 2020. Visit 2: 14 December 2020–29 January 2021.
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