More than two-thirds of Africans have been infected by COVID-19 since the pandemic started – 97 times more than reported confirmed cases, according to a World Health Organization (WHO) study.
The assessment, which is under peer review, and is based on about 150 studies published in 2020 and 2021, shows how under-reported the impact on the world’s poorest may have been.
By September last year, 800m Africans had been exposed to SARS-CoV-2, the virus that causes COVID-19, compared with the 8.2m cases reported at that time, the study found.
WHO says that undercounting happened everywhere, but to a lesser degree than in Africa. On average globally, infections were 16 times higher than confirmed cases.
The agency’s regional director for Africa, Dr Matshidiso Moeti, is quoted in Daily Dispatch as saying that the continent’s high exposure to the virus and declining infection rates did not mean that Africa could declare victory against COVID-19.
“The risks of more lethal variants emerging, which overwhelm immunity gained from past infections, cannot be brushed aside,” she said, calling for increased testing.
The study consisted of synthesising 151 previous studies on seroprevalence in Africa, the proportion of individuals with SARSCoV-2 antibodies in their blood serum.
It found that exposure to the virus had rocketed from 3% in June 2020 to 65% in September 2021, with sharp rises after the emergence of the Beta and Delta variants.
While routine diagnostic testing in Africa focused on travellers and people who present at hospitals with symptoms, seroprevalence studies provide data on asymptomatic cases that otherwise go undetected.
Africa has a higher proportion of asymptomatic cases than other parts of the world, with 67% of cases having no symptoms, the WHO said. That is partly due to a smaller proportion of people with risk factors such as diabetes and hypertension, and partly due to the continent’s youthful population.
While the pandemic has had a catastrophic effect on some parts of the globe, Africa appeared to have escaped the worst and was not as badly hit as initially feared at the start of the outbreak.
With weak health facilities and services, many experts had feared the systems would be overwhelmed, reports Polity. Several analyses have been made of the pattern of the pandemic in Africa, with some concluding that the continent’s youthful population acted as a buffer against severe illness.
The WHO had last year already cautioned that six of every seven COVID infections went undetected in Africa, which has so far fully vaccinated only 209m people, or 16% of the population, against COVID-19.
Studies estimate that 45% of the global population had been infected by September 2021, but the WHO said comparisons were difficult as studies covered different time periods.
Study details
SARS-CoV-2 infection in Africa: A systematic review and meta-analysis of standardised seroprevalence studies, from January 2020 to December 2021
HC Lewis, VH Ware, M Whelan, L Subissi, VZ Li, X Ma, A Nardone, M Valenciano, B Cheng, K Noel, C Cao, M Yanes-Lane, B Herring, A Talisuna, N Nsenga, T Balde, DA Clifton, M Van Kerkhove, DL Buckeridge, N Bobrovitz, J Okeibunor, RK Arora, I Bergeri, the UNITY Studies Collaborator Group
Published on medRXiv on 15 February 2022
Abstract
Introduction
Estimating COVID-19 cumulative incidence in Africa remains problematic due to challenges in contact tracing, routine surveillance systems and laboratory testing capacities and strategies. We undertook a meta-analysis of population-based seroprevalence studies to estimate SARS-CoV-2 seroprevalence in Africa to inform evidence-based decision making on Public Health and Social Measures (PHSM) and vaccine strategy.
Methods
We searched for seroprevalence studies conducted in Africa published 01-01-2020 to 30-12-2021 in Medline, Embase, Web of Science, and Europe PMC (preprints), grey literature, media releases and early results from WHO Unity studies. All studies were screened, extracted, assessed for risk of bias and evaluated for alignment with the WHO Unity protocol for seroepidemiological investigations. We conducted descriptive analyses of seroprevalence and meta-analysed seroprevalence differences by demographic groups, place and time. We estimated the extent of undetected infections by comparing seroprevalence and cumulative incidence of confirmed cases reported to WHO. PROSPERO: CRD42020183634.
Results
We identified 54 full texts or early results, reporting 151 distinct seroprevalence studies in Africa Of these, 95 (63%) were low/moderate risk of bias studies. SARS-CoV-2 seroprevalence rose from 3.0% [95% CI: 1.0-9.2%] in Q2 2020 to 65.1% [95% CI: 56.3-73.0%] in Q3 2021. The ratios of seroprevalence from infection to cumulative incidence of confirmed cases was large (overall: 97:1, ranging from 10:1 to 958:1) and steady over time. Seroprevalence was highly heterogeneous both within countries – urban vs. rural (lower seroprevalence for rural geographic areas), children vs. adults (children aged 0-9 years had the lowest seroprevalence) – and between countries and African sub-regions (Middle, Western and Eastern Africa associated with higher seroprevalence).
Conclusion
We report high seroprevalence in Africa suggesting greater population exposure to SARS-CoV-2 and protection against COVID-19 disease than indicated by surveillance data. As seroprevalence was heterogeneous, targeted PHSM and vaccination strategies need to be tailored to local epidemiological situations.
Daily Dispatch Pressreader article – Two-thirds of Africans infected by COVID-19 (Open access)
Polity article – WHO: Two-thirds of people in Africa may have had Covid (Open access)
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