Time Course of COVID-19 epidemic in Algeria: Retrospective estimate of the actual burden

Since December 2019, the five continents have been incrementally invaded by SARS-CoV-2. Africa is the last and least affected to date. However, Algeria is among the first countries affected since February 25, 2020. In order to benefit from its experience in the least affected countries, this study aims to describe the epidemic’s current situation and then retrospectively estimate its real burden.

As a first part of the study, we described the epidemic’s indicators as; the cumulative and daily reported cases and deaths, and we computed the R0 evolution. Secondly, we used the New York City cases-fatality rate standardized by Algerian age structure, to retrospectively estimate the actual burden.

We found that reported cases are in a clear diminution, but, the epidemic epicentre is moving from Blida to other cities. We noted a clear peak in daily cases-fatality from March 30, to April 17, 2020, Fig. 3, due to underestimating the actual infections of the first 25 days. Since May 8, 2020, the daily R0 is around one, Fig. 4. Moreover, we noticed 31% reduction of its mean value from 1,41 to 0,97 between the last two months. The Algerian Age-Standardized Infection Fatality Rate we found is 0,88%. Based on that, we demonstrated that only 1,5% of actual infections were detected and reported before March 30, and 20% after March 31, Fig. 5. Therefore, the actual infections burden is currently five times higher than reported. At the end, we found that at least 0,2 % of the population have been infected until May 27. Consequently, the acquired herd immunity to date is therefore not sufficient to avoid a second wave.

We believe that, the under estimation of the epidemic’s actual burden is probably due to the lack of testing capacities, however, all the indicators show that the situation is currently controlled. This requires more vigilance for the next weeks during the gradual easing of the preventive measures.