Are we heading for an eighth wave? According to the latest figures published by Santé Publique France, 19,517 positive cases for Covid-19 were recorded on Saturday September 10, 2022, compared to 16,399 on Friday September 2, 2022, an increase of more than 25% in one week. Declining since July, the number of new contaminations identified in 24 hours has therefore increased slightly in recent days in France. Is this the start of a new wave?
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“It is almost certain that we are going to have an eighth wave. With the mixing linked to the return of the holidays, the circulation of the virus will be on the rise”, advances to L’Express Yannick Simonin, virologist, lecturer in surveillance and study of emerging diseases at the University of Montpellier. Among the regions most affected by the resumption of the epidemic, Brittany posted a positivity rate of 22.7% this week. Behind, New Aquitaine (19.2%) and Pays de la Loire (19.6%) are also experiencing a sharp increase in contamination. Nationally, the incidence rate – number of cases per week per 100,000 population – stood at 168 as of September 6. As a reminder, the alert threshold set by the government is 50.
What will this eighth wave look like? “If we refer to the previous ones, there was a very large number of cases, but the hospital impact remained lower. Thanks to past infections and vaccination, the degree of protection within the population is more high”, replies the specialist. It also recalls the arrival of new vaccines adapted to Omicron. The European Medicines Agency (EMA) gave the green light on Thursday, September 1, for the use of two latest generation vaccines against Covid-19, produced by the firms Moderna and Pfizer-BioNTech.
Who will be the future dominant variant?
It remains to be seen who will be the driving force behind this renewed epidemic. For the moment, the Omicron BA.5 variant, which has been the majority in France since the beginning of the summer, represents (if we include the sub-lineages) 95% of the cases in the August 16 Flash sequencing survey. Each new wave being accompanied by a new majority variant, several candidates are expected to take over: the future dominant variant could be a BA.5 sub-lineage, another Omicron sub-lineage or another variant. According to Yannick Simonin, the last hypothesis remains unlikely: “We have not seen the appearance of a new variant outside the Omicron line. reassuring.”
If it was a BA.5 sub-lineage, Santé Publique France wants to be reassuring: “To date, no BA.5 sub-lineage seems to have any particular characteristics”, reassures the institution. Thus, if a sub-lineage of BA.5 takes over in France, it would not at this stage present a risk of being more transmissible or more dangerous.
The other hypothesis is to see another sub-lineage of Omicron take over its competitors. This summer, attention focused on the Omicron BA.2.75 variant, already detected in India, Japan, the United States, Germany and the United Kingdom, among others. Across the Channel, the number of cases of this sub-variant nicknamed “Centaur” had increased sharply, and represented a major risk this summer. Already last June, Tom Peacock, a virologist at Imperial College London, tweeted that BA.2.75 was “worth watching” because it contains “lots of cutting-edge mutations”.
“BA.2.75 has a transmission advantage between 50 and 70%”
What a difference with “his big brother” BA. 2? It has nine additional mutations in the Spike protein, which helps the virus enter human cells, potentially making it more transmissible or increasing its immune escape. “BA.2.75 has a transmission advantage of between 50 and 70% compared to BA.5”, resumes Yannick Simonin. However, no increased virulence or increased risk of hospitalization was observed in him. For now, this is one of the most watched variants. Not very present in France, the information concerning it remains relatively recent and incomplete.
Another variant in the viewfinder of scientists: BA.4.6 which presents an additional mutation compared to BA.4 and BA.5: R346T. Will this be enough to allow him to become dominant? Only a few mutations separate it from its predecessor, but it is slowly gaining ground in the United States. According to the latest data from the United States Public Health Agency (CDC), the BA.4.6 subvariant continued to gain ground this week, now accounting for around 8.4% of Covid-19 cases.