The progression of the COVID-19 pandemic in French-speaking sub-Saharan Africa is not as rapid as feared. What are the hypotheses?
The day-by-day analysis of the progression curve of an epidemic is very informative: appearance of the first cases, peak, decline and disappearance. This is the usual profile of a respiratory virus epidemic. Can we compare African countries to others? There should be a single, universal way of collecting and expressing epidemiological data. At the very least, we need to get countries to share their methods of calculation. The World Health Organization (WHO) has been criticised for failing to provide reliable information on this subject (1), despite the ratification of the International Health Regulations in 2005 following the lessons of the SARS epidemic.
African progression curves:
Lorsqu’on se base sur les résultats apportés par les pays, tels qu’ils sont affichés jour après jour à partir des informations OMS / AFP / Gouvernements et autorités sanitaires des pays concernés, on est interpellé par les profils des courbes en Afrique lorsqu’on les compare à l’Europe :
Based on the results provided by the countries, as they are displayed day after day based on information provided by WHO / AFP / Governments and health authorities of the countries concerned, the profiles of the curves in Africa are surprising when compared to Europe:
In France, the first case of SARS-CoV-2 infection is thought to have been reported on January 29 (to be confirmed). The most important cluster was reported after a religious gathering in Mulhouse between February 17 and 24. The epidemic then had an "exponential", not to say explosive, growth. To observe its evolution, the French National Public Health Agency has been publishing detailed data daily, compiled from information provided by all hospitals in the territory. The peak was observed on March 31 (7578 new cases). If we look at the total number of cases in relation to dates voluntarily chosen to be comparable with a few African countries: there were 191 confirmed cases (including 3 deaths) on March 2, 56,989 cases (including 4,032 deaths) on April 1st, 114,657 cases (12,513 deaths) on April 20, 129,581 cases (15,244 deaths) on April 30, bearing in mind that absolute lockdown had been in place for 6 weeks. Cases from retirement homes were subsequently added, but there are unaccounted cases of patients remaining at home, suggesting an underestimation.
Let's first look at two African countries during the same period and on the same dates:
Senegal had its first case on March 2 (thus with a delay of about a month with France), 190 cases on April 1st, 347 cases on April 20, 933 cases (9 deaths) on April 30, 1182 (still only 9 deaths) on 4 May. The curve is therefore very different, more flattened. The number of deaths is low. In theory, the peak (if it occurs at 2 months) is relatively close.
Cameroon is the most affected country in French-speaking Africa with its first case on March 6. On April 1st it had 233 cases, 1016 cases on 20 April, 1832 cases (including 61 deaths) on 30 April and 2077 cases (64 deaths) on May 4. Although growth is a little faster than in Senegal, it is much slower than in Europe. For these two countries, the number of new cases per day was around one hundred per day but has recently dropped.
Without wanting to provide new figures, the number of new daily cases in countries affected relatively early on, such as Burkina Faso, is relatively low (little changed in the last week: 645 in total (on May 1st), 662 on May 4). Madagascar, which had only 24 cases at the end of March (on 28th), had only 128 cases at the end of April and 149 on May 4. Confirmed cases in other countries as of May 4 are relatively low, except perhaps Ivory Coast (1398) and Guinea (1650): DRC (682), Mali (593), Gabon (335), Benin (96), while the first case was confirmed on March 12, Togo (124), Congo-Brazzaville (229), Chad (117).
The increase in the number of new cases did not accelerate between 4 and 7 May.
After analysing all results from the countries of West and Central Africa and Madagascar, we come to the same conclusion: the epidemic seems to be developing in a completely different way and with a much less threatening evolution than in Europe or the USA on the African continent south of the Sahara. It should be remembered that the most affected country, South Africa, had only 5647 cases (103 deaths) on April 30.
It would also be interesting to have detaailed hospital data from French-speaking African countries. Do they corroborate the statements from the health authorities?
One can also wonder about the number of reported deaths. The percentage of deaths is around 2%, a lower figure than in the rest of the world (6%). It is low in Senegal (only 9) and even in Cameroon (64). In Africa as a whole, there were 40,575 confirmed cases on May 4, including 25,492 patients still hospitalised with 1692 deaths (3). Between May 4 and 7, the number of deaths varied little, 13 in Senegal and 108 in Cameroon.
While seems like good news, how is it that there are fewer cases in Africa when total lockdown except for essential activities is impossible? Cameroon has left its bars and restaurants open until 6pm and only gatherings of more than 50 people are prohibited. Wearing a mask has been compulsory since April 13. In Dakar, there is a curfew but the markets have remained open as usual... The population genetic hypothesis is ruled out: we have already stressed that Blacks are impacted like other populations or even more affected (see statistics of the epidemic in the USA).
What to think?
- The main bias would be insufficient screening due to a lack of declarations:
- because of a lack of medical personnel or health workers in the hinterland,
- for lack of diagnostic tests, accessibility, reliability,
- due to public reluctance,
- if all the actual data is not disclosed (unlikely in our opinion even though social networks can sometimes evoke it).
Demographic data are important to consider and certainly play a role: the African population is much younger (65% would be less than 30 years old) and life expectancy at birth is barely above 62 years in Black Africa (63, 20 in Senegal, 62, 30 in Cameroon) while it is around 82 years in Europe (82.20 in France); however, this figure also depends on the higher infant mortality in Africa (2). Is the youthfulness of the population the only factor?
A climatic influence? This is a well-known fact in the epidemiology of other respiratory viruses. But the evidence is contradictory in a review of scientific studies (3), and this does not allow us to hope for an improvement with summer heat in Western countries, and therefore in hot intertropical climates.
Does the prevalence of infectious diseases specific to these same hot countries, particularly the high incidence of malaria among the African population, represent a reduction in the risk of epidemics? The discussion remains open, and also on the possible influence of traditional treatments and chloroquine. These are widely used therapies. Our group is currently analysing them.
- A reasonable hope: every epidemic has a natural cycle. It will soon be known whether the peak is found to be low in African countries, which would confirm our favourable impression. Indeed, an epidemic most often loses its transmissibility and virulence as it spreads. For this pandemic, it is known that SARS-Cov-2 is undergoing mutations but so far without changing its pathogenic behaviour. Unknowns therefore persist and this calls for caution. At what point can the pandemic completely disappear at global level? Let us dare to use a metaphor of hope: will Africa be its "elephants graveyard?".
- But there is a risk linked to the characteristics of certain epidemics such as influenza: there may be seasonality. Some experts fear a return to Europe in autumn or winter.
This type of critical situation could only be resolved by the creation and availability (non-commercial...) of an effective vaccine. So this hope must be tempered.
The worst-case scenario of an uncontrollable pandemic in large cities and in the hinterland seems to be a possibility that can be ruled out in the light of developments. A choice must be made between caution and confidence. What is to be done? After several weeks of alert, some African countries are considering the gradual lifting of certain preventative measures following a favourable assessment of the epidemiological indicators in their possession. There may be a transitory rebound. This early decision is not approved by the WHO, which also calls for maintaining strong control measures to fight the spread of the new coronavirus on the continent (4). We have already mentioned the impossibility of the strongest measures (total lockdown).
In conclusion: prudent optimism.
Propos colligés par Jacques Barrier (France) Professeur émérite Université de Nantes (France) ancien Président du Conseil pédagogique de la CIDMEF, ancien président de la Fédération des Spécialités Médicales (France)