Skip to main content

High prevalence of anti-SARS-CoV-2 antibodies after the first wave of COVID-19 in Kinshasa, Democratic Republic of the Congo: results of a cross-sectional household-based survey

Our take —

A population-based serosurvey was conducted using random household-based sampling in Kinshasa, Democratic Republic of Congo from October 2020 to November 2020. Of those participating in the study, 16.6% tested positive for SARS-CoV-2 antibodies, suggesting a substantial undercounting of the true number of SARS-CoV-2 infections compared to the number of cases reported by the national health surveillance system. Findings should be interpreted with some caution as close to half of those eligible were not included in the final analyses, potentially under- or overestimating the prevalence, depending on whether those at home were more or less likely to be previously infected.

Study design

Cross-Sectional

Study population and setting

Between October 22, 2020 and November 8, 2020, a cross-sectional, household-based serosurvey was conducted to assess the prevalence of SARS-CoV-2 IgG antibodies in Kinshasa, Democratic Republic of the Congo. A sampling frame was constructed using health divisions of the city; random sampling was done based on a three-stage probability proportional-to-size sampling strategy. Venous blood samples were collected from all available participants and a Luminex-based assay was used to detect IgG antibodies against both SARS-CoV-2 nucleocapsid and spike proteins. A positive serology was based on reactivity to both SARS-CoV-2 proteins. Using a smartphone application, participants answered questions regarding their household members, symptoms, socioeconomic status, and behaviors. The seroprevalence estimate was weighted and age-standardized based on demographic data.

Summary of Main Findings

Among 1,233 participants from 292 households, the weighted, age-standardized estimate of seroprevalence was 16.6% (95% CI: 14.0-19.5). An additional 17.1% were considered “indeterminate,” as their test was shown to be reactive to one of the two SARS-CoV-2 proteins. Nearly three of every four participants shared a common yard space (72.2%, 890/1,233), as opposed to living in a single family home, and over half did not have access to handwashing at home (54.2%, 668/1,233). Based on the measured prevalence, the authors estimated that there had been a total of 2,426,406 infections in Kinshasa , which would indicate that for every one case identified through the health surveillance system, there were 292 cases that were not diagnosed.

Study Strengths

The use of random probability proportional-to-size sampling is a strength because this study likely represents the population-based prevalence better than a study conducted in a specific population group.

Limitations

A total of 2,400 individuals were eligible for the study. Of these, 1,607 were present at the time of the enrollment and 1,233 were included in the final analysis. Therefore, the proportion of eligible participants included in the final analysis was 51%. By only enrolling such a limited proportion of all eligible individuals, this study may not be representative of the entire population of Kinshasa. As a result, the true population-based prevalence may be biased downward or upward, depending on whether those previously infected were more or likely to enroll; such bias would also influence the calculated ratio of reported cases to true infections.

Value added

This is one of the first studies to assess seroprevalence in the African context in the general population. Past serosurveys have primarily been conducted among specific population groups (e.g. healthcare workers). This study helps shed light on the discrepancy between reported cases and the true number of cases.

This review was posted on: 27 June 2021