Does France still have the means to follow the galloping evolution of the Omicron variant on its soil?
Guillaume Rozier, datascientist at the origin of the CovidTracker site, which makes it possible to follow the figures of the pandemic, and ViteMaDose, which makes it possible to reserve a vaccination window, was moved on Twitter that CovidTracker would no longer be able to document the circulation of the Omicron variant.
The reason: a change in methodology in screening samples for positive coronavirus tests.
Read alsoThe new French surveillance strategy complicates the monitoring of the Omicron variant
The CovidTracker site uses public data from the data.gouv.fr site to feed its visualizations concerning the circulation of the virus.
However, while the government site has so far indicated the data resulting from the screening of part of the positive samples taken in France, the reporting of these data has diminished, to the point where they have become difficult to use.
A problem which was already alarmed by Florence Debarre, researcher at the CNRS, before Christmas.
Until November, the screening tests aimed to detect certain mutations of the virus: E484K, E484Q and L452R, with the respective code A, B and C. Delta carrying the C mutation, the monitoring of this mutation could for example make it possible to follow the circulation of this variant among the French.
“
By pure chance or luck, Omicron does not have this C mutation, unlike Delta.
Monitoring the proportion of cases without C therefore allowed us to have a good approximation of Omicron cases
, ”explains Guillaume Rozier.
To read also "The feeling that one will never see the end": the hospital facing the challenge of the breaking Omicron
"
Broken thermometer
"
However, to refine this monitoring, Public Health France explained that since December 20, 2021, the screening integrates the monitoring of mutations which are specific to the Omicron variant, "
such as the 69/70 deletion and the substitutions K417N, S371L-S373P and Q493R
" . A new code, D, must therefore be added to the three previous ones to allow medical biology laboratories to include in screening results the presence of mutations specific to Omicron.
This measure had the effect of causing a drop in the screening results.
Certain laboratories have in fact continued to transmit their results according to the old system - A, B, C - while others are now based on the new operation, which includes the code D. Public Health France for its part still publishes the results. data under the old system.
The imbroglio is such that now, "
the thermometer is broken
", and this at the worst moment since the Omicron variant continues to spread at full speed, deplores Guillaume Rozier.
Read alsoFaced with Omicron, are antigenic tests still reliable?
Santé Publique France, for its part, ensures that the problem should be resolved "
quickly
", to once again allow reliable monitoring of the evolution of the variant.