Paris, Aug. 15 (EIRNS) – In an op-ed published on July 24, by French publication La Tribune, three prominent French scientists explain why the pandemic doesn’t appear on the radar in Africa. Their argument is that the level of confirmed Covid-19 cases reported in Africa is very low. With some 6.3 million infections and 160,000 deaths recorded, the number of cases officially reported by the African Centers for Disease Control and Prevention seems to indicate that SARS-CoV-2 is not spreading very widely in Africa: on a continental scale, the prevalence of its infection is less than 1%. “However, the story told by the first results of seroprevalence studies, which estimate the proportion of people who have come into contact with the virus by detecting antibodies in their bodies, is very different,” argue the scientists. “Sampling and analysis of various populations (blood donors, caregivers, general population, etc.) indicate a high prevalence of SARS-CoV-2 infection, averaging around 20% and up to 60% depending on the location…. The spread of SARS-CoV-2 in Africa could therefore be much higher than previously thought.”
To elude this gap and explain why the real situation is not on the radar, they give several reasons. First, the use of serological diagnostic tests lacking both efficiency and specificity:
Respecting specificity: “A test that performs well in one setting (e.g., in a particular geographic environment) may perform poorly in another. This is particularly a problem when tests have been developed in a different context from the one in which they are used, as they may give incorrect results compared to reality. At a minimum, a serological test used in Africa should have been validated on samples from people living in Africa. However, some serological tests used in Africa have not been validated on blood samples from people living on the continent,” the scientists complain.
Respecting efficiency: “The final important test element to consider in SARS-CoV-2 serology is the antigen detected by the test. Most tests detect only one antigen, either the S or N protein. However, antibodies to these two antigens appear and disappear at different times during infection and last for different lengths of time. In addition, these proteins have more or less important similarities with the proteins of other coronaviruses, in particular seasonal ones, which can falsify the tests.”
To overcome potential biases and provide more accurate estimates of incidence, the joint research unit, TransVIHMI has developed a test that simultaneously detects antibodies to the two main SARS-CoV-2 antigens (N and S), with a strict positivity criterion.
So far “Three explanations are generally advanced to explain the epidemic dynamics on the African continent. The first is demography. On the African continent, 60% of the population is under 25 years of age, with only 3.5% of the population over 65 years of age. It is known that age is a determining factor in the severity of Covid-19 and the risk of mortality. This may explain why the African population has not been affected by excess mortality to the extent that Western Europe, where 20% of the population is over 65, has been. The relative youth of the population may not only have limited the number of severe cases, but may also have resulted in a large number of asymptomatic cases, which may partly explain the low number of officially reported cases.
“The second explanation for the apparent paradox between reported cases and seroprevalence results could be the low case detection capacity on the African continent, which does not allow for systematic screening.
“Finally, a third explanation is that the existence of cross-immunity induced by other coronaviruses, or even other pathogens, circulating on the continent cannot be excluded. This could limit the number of severe cases by conferring immunity to SARS-CoV-2 in a manner similar to that conferred by vaccination. Some studies currently underway in Sub-Saharan Africa will help answer this question: serological tests incorporating markers of other coronaviruses have been developed to identify such cross-immunity reactions if they exist.” (https://www.latribune.fr/opinions/tribunes/que-sait-on-de-la-propagation-du-covid-en-afrique-889602.html)
