Retrospective mortality and prevalence of SARS-CoV-2 antibodies in greater Omdurman, Sudan: a population-based cross-sectional survey

Moser, W.; Fahal, M. A. H.; Abualas, E.; Bedri, S.; Taj Elsir, M.; Mohamed, M. F. E. R. O.; Mahmoud, A. B.; Ahmad, A. I. I.; Mohammed, M. A.; Altalib, S.; DafaAllah, O. A.; Hmed, S. A.; Azman, A. S.; Ciglenecki, I.; Gignoux, E.; Gonzalez, A.; Mwongera, C.; Albela, M.

Background Even after adjusting for the expected lower severity due to the younger age of the population, relatively low SARS-CoV-2 incidence and mortality rates have been reported throughout Africa. For investigating whether this is truly the case, we conducted a survey to estimate the COVID-19 related mortality and cumulative incidence of SARS-CoV-2 infections in Omdurman the most populated city of the tripartite metropolis Khartoum in Sudan. Methods A retrospective, cross-sectional, mortality and seroprevalence survey was conducted in Omdurman, Sudan, from March 1, until April 10 2021. A two-stage cluster sampling method was used to investigate the death rate for the pre-pandemic (January 1, 2019-February 29, 2020) and pandemic (March 1, 2020 - day of the survey) period using questionnaires. The seroprevalence survey was performed in a subset of households and all consenting members were tested with a rapid serological test (SD-Biosensor) and a subgroup additionally with ELISA (EUROIMMUN). Fisher's exact test was used to assess differences between the pre-and pandemic periods and a random effect and Bayesian latent class model to adjust for test performance. Findings Data from 27315 people (3716 households) for the entire recall period showed a 67% (95% CI 32-110) increase in death rate between the pre-pandemic (0.12 deaths/10000 people/day [95% CI 0.10-0.14]) and pandemic (0.20 [0.16-0.23]) periods. Notably, a 74% (30-133) increase in death was observed among people aged [≥]50 years. The adjusted seroprevalence of SARS-CoV-2 was 54.6% (95% CI 51.4-57.8). The seroprevalence was significantly associated with age, increasing up to 80.7% (71.7-89.7) for the oldest age group ([≥]50 years). Interpretation Our results showed a significant elevated mortality for the pandemic period with a considerable excess mortality in Omdurman, Sudan. The overall high seroprevalence indicated a different age pattern compared to other countries, with a significant increase by age. Funding Medecins Sans Frontieres