Intense and Mild First Epidemic Wave of Coronavirus Disease, The Gambia

Abstract

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is evolving differently in Africa than in other regions. Africa has lower SARS-CoV-2 transmission rates and milder clinical manifestations. Detailed SARS-CoV-2 epidemiologic data are needed in Africa. We used publicly available data to calculate SARS-CoV-2 infections per 1,000 persons in The Gambia. We evaluated transmission rates among 1,366 employees of the Medical Research Council Unit The Gambia (MRCG), where systematic surveillance of symptomatic cases and contact tracing were implemented. By September 30, 2020, The Gambia had identified 3,579 SARS-CoV-2 cases, including 115 deaths; 67% of cases were identified in August. Among infections, MRCG staff accounted for 191 cases; all were asymptomatic or mild. The cumulative incidence rate among nonclinical MRCG staff was 124 infections/1,000 persons, which is >80-fold higher than estimates of diagnosed cases among the population. Systematic surveillance and seroepidemiologic surveys are needed to clarify the extent of SARS-CoV-2 transmission in Africa.

Keywords: Africa; COVID-19; SARS; SARS-CoV-2; The Gambia; coronavirus; coronavirus disease; disease burden; severe acute respiratory syndrome coronavirus 2; severity respiratory infections; transmission rate; viruses; zoonoses.

Figure 1

Population density of The Gambia, including Medical Research Council Unit The Gambia (MRCG) research sites distributed across the country.

Figure 2

Number of daily nasopharyngeal and oropharyngeal swab samples tested for severe acute respiratory syndrome coronavirus 2 and percentage of positive samples in The Gambia during August–September 2020, the timeframe for the most intense transmission in the country.

Figure 3

Daily COVID-19 cases and cumulative rates of SARS-CoV-2 infection per 1,000 persons among staff of Medical Research Council Unit The Gambia (MRCG) and the population of The Gambia, June 30–October 1, 2020. A) Case rates for MRCG staff outside the clinical service department and the population of The Gambia. We considered MRCG staff outside the clinical service department to be at the same risk for COVID-19 as the rest of the population. B) Risk for SARS-CoV-2 infection among MRCG staff stratified by potential occupational exposure risk. We considered clinical service department staff at highest risk for SARS-CoV-2 infection, and these staff were under more intense surveillance. Scales for the y-axes differ substantially to underscore patterns but do not permit direct comparisons. COVID-19, coronavirus disease; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.