From Beta to Alpha, via Delta or even Omicron… in two years, SARS-CoV-2 has, like any virus, undergone multiple mutations. If today “all the virological indicators indicated[e] a decrease in the circulation of SARS-CoV-2 on the national territory”, writes Santé Publique France in its last weekly epidemiological update dated April 28, the emergence of new sub-variants of Omicron throughout the world encourages the Two newcomers have just made their appearance in South Africa: BA.4 and BA.5, which follow on from BA.1, BA.2 and BA.3.
The country’s health situation, which has seen the appearance of the Delta and Omicron variants, is particularly followed by epidemiologists around the world because the emergence of these new “sub-lineages” of Omicron could well have repercussions on European territory. “When the last wave of Omicron BA.1 swept through South Africa last November and December (and peaked in mid-December), it didn’t take a month and a half before it does not sweep over France and Europe”, explains to L’Express Antoine Flahault, medical epidemiologist and director of the Institute for Global Health at the University of Geneva.
“We had too quickly declared that Omicron was benign and it is true that vaccinated and non-immunocompromised people were well protected from severe forms of Covid-19, but the very high transmissibility of the variant led to a level of mortality equivalent in number absolute to that reported during the first year of the pandemic (65,000 deaths in 2020 and 22,000 deaths for the first four months of 2022 alone in France), adds the researcher. So, yes, the emergence of new highly transmissible variants in South Africa is cause for concern.”
Still very few cases in France
According to the authors ofa South African study published on April 28 on the website of the Center of Epidemic Response and Innovation (CERI) at Stellenbosch University, BA.4 and BA.5 respectively emerged in southern Africa in mid-December and early January before becoming dominant in the country from April. In mid-April, they represented around 60 to 75% of the cases sequenced in South Africa, a country particularly well equipped with virus sequencing tools.
BA.4 and BA.5 have also been identified in Belgium, Denmark, Germany and the United Kingdom, according to the World Health Organization (WHO). In France, the health authorities have identified a case of contamination with BA.4, linked to a trip to South Africa, and two carriers of BA.5. If these sub-variants are subject to “reinforced surveillance on the basis of their genetic profile” explains Public Health France in its risk analysis related to emerging variants dating from April 20, at this stage “no worrying epidemiological or clinical element is associated with them”. In mid-April, Dr Matshidiso Moeti, WHO Regional Director for Africa wanted to be rather reassuring: “There is no need to be alarmed with the emergence of new sub-variants We are not yet seeing a major spike in cases, hospitalizations or deaths.”
Probably more contagious variants
If the situation does not seem to be worrying for the moment, it could very well change in the weeks to come. “At the beginning, it is rather the young working people and the mobile segments of society who are infected. These are not the groups that are most at risk of ending up in hospital, analyzes Antoine Flahault. It therefore takes several weeks for the infections are affecting another audience and are starting to weigh on the country’s statistics”.
According to Public Health France, these two sub-lineages are “quite similar to BA.2 but their Spike protein additionally has the L452R, F486V and R493Q mutations”. These mutations “suggest a possible immune escape and greater transmissibility”, explains Antoine Flahault. As confirmed by the European Center for Disease Prevention and Control (ECDC), several elements therefore suggest that BA.4 and BA.5 could have a “significant impact on transmissibility, severity and/or immunity”, but it is still too early to draw conclusions, the evidence is still “partial” or “associated with high uncertainty”.