Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 28, Number 6—June 2022
Dispatch

Rapid Increase of Community SARS-CoV-2 Seroprevalence during Second Wave of COVID-19, Yaoundé, Cameroon

Author affiliations: Ministry of Public Health of Cameroon Division of Operational Research in Health, Yaoundé, Cameroon (F. Ateba Ndongo, J. Ndié, F.N. Tabala, R.K. Dongmo, A.-C. Zoung-Kanyi Bissek); Recherches Translationnelles sur le VIH et les Maladies Infectieuses, University of Montpellier, Institut de Recherche pour le Développement, Institut National de la Santé et de la Recherche Médicale, Montpellier, France (E. Guichet, R. Pelloquin, M.S.K. Diallo, J. Bouillin, G. Thaurignac, A. Ayouba, M. Peeters, E. Delaporte); French National Agency for Research on AIDS and Infectious Diseases, Cameroon Site, Central Hospital of Yaoundé, Yaoundé (E.D. Mimbé, M. Varloteaux, A.-C. Zoung-Kanyi Bissek, E. Mpoudi-Ngolé); Centre de Recherche sur les Maladies Emergentes et Réémergentes, Yaoundé (L. Esemu, N. Lamare, G. Edoul, R. Kamga Wouambo, D. Meta Djomsi, M. Tongo, E. Mpoudi-Ngolé); Military Hospital of Yaoundé, Yaoundé (M. Mpoudi-Etame)

Cite This Article

Abstract

We conducted 2 independent population-based SARS-CoV-2 serosurveys in Yaoundé, Cameroon, during January 27–February 6 and April 24–May 19, 2021. Overall age-standardized SARS-CoV-2 IgG seroprevalence increased from 18.6% in the first survey to 51.3% in the second (p<0.001). This finding illustrates high community transmission during the second wave of COVID-19.

Since the recognition of the first cases of COVID-19 at the end of 2019 in Wuhan, China, SARS-CoV-2 has spread rapidly across the globe. By late November 2021, almost 260 million confirmed cases, including at least 5 million deaths, had been reported (1). Cases from Africa represent only 3.4% of those cases worldwide (1,2), but serologic surveys demonstrate that the extent of SARS-CoV-2 spread in Africa is higher (3). After the first pandemic wave, overall seroprevalence in Africa was estimated at ≈22%, ranging from <1% to >70% depending on country and study population (3). The few studies reporting data after the second wave in Africa demonstrated a rapid increase to >50% seroprevalence (46). Underestimation of COVID-19 cases was most likely caused by weak healthcare infrastructure, low or no access to diagnostic testing, and higher proportions of paucisymptomatic or asymptomatic disease related to younger population or cross-reactive immunity from other coronavirus infections. The overall objective of our study was to evaluate the effect of the second wave of COVID-19 on SARS-COV-2 seroprevalence in the general population of Yaoundé, the capital city of Cameroon.

The Study

We conducted 2 population-based seroprevalence surveys in Yaoundé during January 27–February 6, 2021 (survey 1) and April 24–May 19, 2021 (survey 2). We adapted the study design from the World Health Organization population-based age-stratified seroepidemiologic investigation protocol for COVID-19 infection, version 2.0 (7). We randomly selected households in 6 of the 7 health districts in Yaoundé, with a probability of being selected proportional to the population number in each enumeration area (Appendix Figure 1). In 50% of households, we invited all residents to participate; among the remaining 50%, we invited only residents >40 years of age. We calculated sample size to estimate overall seroprevalence in Yaoundé. The samples were independent for the 2 surveys. All persons belonging to the selected household were eligible. We scheduled appointments for participants who were absent during the survey. We used individual questionnaires to collect sociodemographic data, medical history associated with COVID-19 symptoms (in the 4 months before the start of the survey), contact with COVID-19 patients, and previous SARS-CoV-2 tests (recall period beginning in March 2020). We offered PCR testing to all participants who were suspected to be SARS-CoV-2–positive. We obtained written consent from all adults and written parental consent for participants <21 years of age (with children’s assent when >10 years of age). The study was approved by the national ethics committee (approval no. 2020/10/1310/CE/CNERSH/SP).

We collected whole blood samples in EDTA tubes and as dried blood spot (DBS) samples for children and other participants who declined to provide venous blood. We eluted DBS samples and used 100 μL of diluted eluate, adjusted at a final plasma dilution of 1/200, as previously validated (Appendix Figure 2), to test for SARS-CoV-2 antibodies with a previously developed, highly sensitive, and specific multiplex assay (Luminex Corporation, https://www.luminexcorp.com) using recombinant nucleocapsid (NC) and spike (SP) SARS- CoV-2 proteins (8). We considered samples positive when they reacted simultaneously with NC and S proteins but considered samples reacting with only 1 antigen indeterminate because of the difficulty discriminating between antibody decline or lower specificity of single-antigen reaction, especially with samples from populations in Africa (9,10). The test was previously evaluated on 1,197 samples from Africa before the COVID-19 pandemic, including 184 from Cameroon, with 99.7% specificity (11).

We performed statistical analysis with Stata 16 (StataCorp, https://www.stata.com). We age-standardized the overall seroprevalence estimate on the basis of available demographic data (12) and tested associations between positive serologic tests and key risk factors with multivariate logistic models and likelihood ratio tests. We used the Pearson χ2 test to compare categorical descriptive outcomes.

In the first survey, 786 (47.7%) of 1,647 eligible participants from 392 households were included. For 722 persons, we obtained sufficient sample volume for antibody testing. To improve participation for the second survey, we strengthened community mobilization, conducted surveys on the weekend, and scheduled appointments for absent participants. In the second survey, 1,234 (85.3%) of 1,447 eligible persons from 424 households were included. Serologic data were available for 1,228 persons. Distribution of sex was comparable between the surveys; the proportion of participants <20 years of age was higher but not significantly so in the second survey (Table 1). Approximately 15% of participants reported a previous diagnostic SARS-CoV-2 PCR test; only 1.3% (1/77) reported a positive test in the first survey and 2.1% (4/194) in the second survey. In both surveys, a limited number of participants (3.3% in the first survey, 4.1% in the second) reported contact with a PCR-confirmed SARS-CoV-2–positive person.

The overall age-standardized SARS-CoV-2 IgG seroprevalence against SP and NC proteins increased from 18.6% (95% CI 15.7%–21.7%) to 51.3% (95% CI 48.3%–54.2%) (p<0.001) during the 3-month period between surveys (Table 2). In both surveys, seroprevalence remained comparable between men and women (Table 2). Seroprevalence increased in all age categories and was significantly higher among persons >20 years of age in both surveys (p = 0.002 for survey 1 and p<0.001 for survey 2). The proportion of persons with SP protein antibodies only (29.1% vs. 16.9%) was higher than those with NC antibodies only (5.8% vs. 5.2%) (Appendix Table 1). We determined population-level distributions of median fluorescence intensity for each of the SARS-CoV-2 antigens (Appendix Figure 3). We found no association between seropositivity and history of symptoms associated with COVID-19 or hospitalization in general before the survey (Appendix Table 2).

Conclusions

In these 2 consecutive population-based SARS-CoV-2 seroprevalence studies, conducted just before the start of the second wave of COVID-19 (January–February 2021) and at its decreasing trend (April–May 2021) (Appendix Figure 4), we found extensive community transmission in Yaoundé, where seroprevalence reached up to 50%. By the end of November 2021, Cameroon reported only 106,749 cases (2), but seroprevalence suggests that by early May 2021, 51% of the population of Yaoundé had antibodies to SARS-CoV-2, corresponding to >2 million persons in the total population of Yaoundé (estimated to be ≈4.1 million). Choice of serologic tests is vital (9), and therefore we used strict criteria and considered seropositivity as presence of antibodies to 2 different SARS-CoV-2 antigens (8,11). We cannot exclude that a proportion of the participants with antibodies against a single antigen also had a previous SARS-CoV-2 infection or were seroconverting (10).

The disparity in numbers of confirmed cases and persons estimated to have SARS-CoV-2 antibodies clearly demonstrates that COVID-19 infections were mainly paucisymptomatic or asymptomatic (1,2). We also observed no association between history of symptoms or hospitalization. Moreover, few persons reported contact with confirmed SARS-CoV-2–positive persons or had received a PCR test. Similar findings were reported in other studies in Africa (46).

Overall, the results of the household SARS-CoV-2 serosurveys during the second COVID-19 wave in Yaoundé, Cameroon, show a high seroprevalence and rapid spread in the general population similar to that observed in other countries in Africa (46,13). The country faced additional waves, and new population-based studies to monitor the evolution of seroprevalences to the different antibodies against SARS-CoV-2 epitopes will be vital. It can also not be excluded that antigens from the different SARS-CoV-2 variants have to be included in future assays, especially against highly divergent variants as illustrated by the emergence of the Omicron variant.

Dr. Ateba Ndongo is a medical doctor and epidemiologist affiliated at the Division of Operational Research at the Ministry of Health in Cameroon. His primary research interests are infectious diseases and management of HIV infections in children and adolescents.

Top

Acknowledgments

We thank all the participants, the investigation teams, the community health staff, and logistical support of DROS/MINSANTE, ANRS-MIE Cameroon Site, and CREMER in the field. We are also grateful to Sébastien Awono Noah and Caroline Coulon.

This work was supported by the Agence Française de Développement and the Ministère de l’Europe et des Affaires Etrangères, France (Project ARIACOV: Appui à la riposte africaine à l’épidémie de COVID-19, https://www.ariacov.org).

Top

References

  1. World Health Organization. Coronavirus (COVID-19) dashboard [cited 2021 Nov 26]. https://covid19.who.int
  2. Africa Centres for Disease Control and Prevention. Coronavirus disease 2019 (COVID-19) [cited 2021 Nov 26]. https://africacdc.org/covid-19
  3. Chisale  MRO, Ramazanu  S, Mwale  SE, Kumwenda  P, Chipeta  M, Kaminga  AC, et al. Seroprevalence of anti-SARS-CoV-2 antibodies in Africa: A systematic review and meta-analysis. Rev Med Virol. 2022;32:e2271. DOIPubMedGoogle Scholar
  4. Sagara  I, Woodford  J, Kone  M, Assadou  MH, Katile  A, Attaher  O, et al. Rapidly increasing SARS-CoV-2 seroprevalence and limited clinical disease in three Malian communities: a prospective cohort study. Clin Infect Dis. 2022;74:10308. DOIPubMedGoogle Scholar
  5. Fryatt  A, Simms  V, Bandason  T, Redzo  N, Olaru  ID, Ndhlovu  CE, et al. Community SARS-CoV-2 seroprevalence before and after the second wave of SARS-CoV-2 infection in Harare, Zimbabwe. EClinicalMedicine. 2021;41:101172. DOIPubMedGoogle Scholar
  6. Kleynhans  J, Tempia  S, Wolter  N, von Gottberg  A, Bhiman  JN, Buys  A, et al.; PHIRST-C Group. PHIRST-C Group. SARS-CoV-2 seroprevalence in a rural and urban household cohort during first and second waves of infections, South Africa, July 2020–March 2021. Emerg Infect Dis. 2021;27:30209. DOIPubMedGoogle Scholar
  7. World Health Organization. Seroepidemiological investigation protocol for coronavirus 2019 (COVID-19) infection [cited 2021 Nov 3]. https://www.who.int/publications/i/item/WHO-2019-nCoV-Seroepidemiology-2020.2
  8. Ayouba  A, Thaurignac  G, Morquin  D, Tuaillon  E, Raulino  R, Nkuba  A, et al. Multiplex detection and dynamics of IgG antibodies to SARS-CoV2 and the highly pathogenic human coronaviruses SARS-CoV and MERS-CoV. J Clin Virol. 2020;129:104521. DOIPubMedGoogle Scholar
  9. Nkuba Ndaye  A, Hoxha  A, Madinga  J, Mariën  J, Peeters  M, Leendertz  FH, et al. Challenges in interpreting SARS-CoV-2 serological results in African countries. Lancet Glob Health. 2021;9:e5889. DOIPubMedGoogle Scholar
  10. Lumley  SF, Wei  J, O’Donnell  D, Stoesser  NE, Matthews  PC, Howarth  A, et al.; Oxford University Hospitals Staff Testing Group. The duration, dynamics, and determinants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody responses in individual healthcare workers. Clin Infect Dis. 2021;73:e699709. DOIPubMedGoogle Scholar
  11. Nkuba  AN, Makiala  SM, Guichet  E, Tshiminyi  PM, Bazitama  Y, Yambayamba  M, et al. 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. Clin Infect Dis. 2022;74:88290. DOIPubMedGoogle Scholar
  12. The World Bank. Cameroon: world development indicators. 2019 [cited 2021 Nov 26]. https://data.worldbank.org/country/cameroon
  13. Mandolo  J, Msefula  J, Henrion  MYR, Brown  C, Moyo  B, Samon  A, et al. SARS-CoV-2 exposure in Malawian blood donors: an analysis of seroprevalence and variant dynamics between January 2020 and July 2021. BMC Med. 2021;19:303. DOIPubMedGoogle Scholar

Top

Tables

Top

Cite This Article

DOI: 10.3201/eid2806.212580

Original Publication Date: April 25, 2022

Table of Contents – Volume 28, Number 6—June 2022

EID Search Options
presentation_01 Advanced Article Search – Search articles by author and/or keyword.
presentation_01 Articles by Country Search – Search articles by the topic country.
presentation_01 Article Type Search – Search articles by article type and issue.

Top

Comments

Please use the form below to submit correspondence to the authors or contact them at the following address:

Emilande Guichet, TransVIHMI, 911 Avenue Agropolis, 34394 Montpellier, France

Send To

10000 character(s) remaining.

Top

Page created: April 03, 2022
Page updated: May 22, 2022
Page reviewed: May 22, 2022
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
file_external