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[Preprint]. 2020 Aug 5:2020.07.30.20164970.
doi: 10.1101/2020.07.30.20164970.

High SARS-CoV-2 seroprevalence in health care workers but relatively low numbers of deaths in urban Malawi

Marah G Chibwana  1 , Khuzwayo C Jere  1   2 , Raphael Kamn'gona  1 , Jonathan Mandolo  1 , Vincent Katunga-Phiri  1 , Dumizulu Tembo  1 , Ndaona Mitole  1 , Samantha Musasa  3 , Simon Sichone  1 , Agness Lakudzala  1 , Lusako Sibale  1 , Prisca Matambo  1 , Innocent Kadwala  1 , Rachel L Byrne  4 , Alice Mbewe  1 , Marc Y R Henrion  1   4 , Ben Morton  1   4 , Chimota Phiri  5 , Jane Mallewa  3 , Henry C Mwandumba  1   4 , Emily R Adams  4 , Stephen B Gordon  1   4 , Kondwani C Jambo  1   4
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High SARS-CoV-2 seroprevalence in health care workers but relatively low numbers of deaths in urban Malawi

Marah G Chibwana et al. medRxiv. .

Update in

  • This article has been published with doi: 10.12688/wellcomeopenres.16188.1

Abstract

Background: In low-income countries, like Malawi, important public health measures including social distancing or a lockdown have been challenging to implement owing to socioeconomic constraints, leading to predictions that the COVID-19 pandemic would progress rapidly. However, due to limited capacity to test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, there are no reliable estimates of the true burden of infection and death. We, therefore, conducted a SARS-CoV-2 serosurvey amongst health care workers (HCWs) in Blantyre city to estimate the cumulative incidence of SARS-CoV-2 infection in urban Malawi.

Methods: We recruited 500 otherwise asymptomatic HCWs from Blantyre City (Malawi) from 22nd May 2020 to 19th June 2020 and serum samples were collected from all participants. A commercial ELISA was used to measure SARS-CoV-2 IgG antibodies in serum.

Results: A total of 84 participants tested positive for SARS-CoV-2 antibodies. The HCWs with positive SARS-CoV-2 antibody results came from different parts of the city. The adjusted seroprevalence of SARS-CoV-2 antibodies was 12.3% [CI 8.2 - 16.5]. Using age-stratified infection fatality estimates reported from elsewhere, we found that at the observed adjusted seroprevalence, the number of predicted deaths was eight times the number of reported deaths.

Conclusions: The high seroprevalence of SARS-CoV-2 antibodies among HCWs and the discrepancy in the predicted versus reported deaths suggests that there was early exposure but slow progression of COVID-19 epidemic in urban Malawi. This highlights the urgent need for development of locally parameterised mathematical models to more accurately predict the trajectory of the epidemic in sub-Saharan Africa for better evidence-based policy decisions and public health response planning.

Keywords: COVID-19; IgG; Malawi; SARS-CoV-2; Seroprevalence.

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Conflict of interest statement

Competing interests E.R.A. and R.L.B. worked with Mologic (UK) to independently validate the SARS-CoV-2 ELISA at the Liverpool School of Tropical Medicine (LSTM). All other authors report no potential conflicts.

Figures

Figure 1.
Figure 1.. SARS-CoV-2 serological results from asymptomatic health care workers.
We used a commercial ELISA to measure SARS-CoV-2 antibodies against Spike (S2) and Nucleoprotein (N). OD, optical density.
Figure 2.
Figure 2.. Map of Blantyre showing geospatial distribution of seropositive results.
We collected geocoordinate data for the place of residence of all study participants at recruitment. The geocoordinates were combined with the ELISA assay results and plotted on the map of Blantyre using R. Black dot, seronegative; Orange dot, indeterminate; Red dot, seropositive.
See this image and copyright information in PMC

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