The BA.2 variant has become the majority in France: here are the scenarios from the Institut Pasteur

The Institut Pasteur carries out modeling the spread of the virus SARS-CoV-2 in France since the start of the pandemic. The last note published dates from March 10, 2022 and attempts to predict the evolution of the French epidemic situation after the relaxation of the measures put in place by the government on Monday March 14. the report is particularly interested in the spread of BA.2 subvariant of the Omicron variant.

BA.2 which has become the majority in France

The Omicron variant represents almost all cases of coronavirus in France. There are four sub-lineages: BA.1, BA.1.1 (sub-lineage of BA.1), BA.2 and BA.3. After having circulated for a long time at low noise, the BA.2 variant has gained momentum in France recently and has become the majority in a few weeks. According to data from Public Health Francethe BA.2 variant represented:

• as of February 14: 25% of cases;
• as of February 21: 43% of cases;
• as of February 28: 52% of cases.

As of February 21, 22% and 34% of cases were related to the BA.1 and BA.1.1 subvariants respectively. Cases of the BA.3 sub-variant are occasionally identified.

An increase in transmission rates

The Institut Pasteur predicts, unsurprisingly, that ” the relaxation of control measures on March 14 should push up transmission rates “. A rise that began even before the date of March 14, suggesting that the French understandably anticipated this date a little. Indeed, the effective R increased and rose to 0.81 at the end of February. For the record, the effective R corresponds to the number of people that an infected person can infect in turn. It shows an acceleration of the epidemic when it exceeds 1.

The Institut Pasteur presents several scenarios, from the most pessimistic to the most optimistic. In any situation, the number of new daily cases should still be well below those of January, at the height of the 5^and wave. As a reminder, the number of new daily cases had reached a peak of 500,000 cases at the end of January. However, it would be possible for this indicator to exceed 100,000 cases per day during the month of March.

The authors of this document hypothesize that people infected with Omicron cannot re-infect themselves with Omicron. Moreover, the progressive decline of immunity is not taken into account in the models. From the beginning of the document, the scientists warn: “ These scenarios are made on the database incomplete and uncertain assumptions. The spread of the SARS-CoV-2 virus is difficult to anticipate; and the dynamics of the epidemic can change rapidly. Vigilance and close monitoring of indicators are therefore required.