Guillaume Rozier, founder of this site for tracking pandemic figures, believes that a upheaval in screening methods no longer allows reliable data to be obtained on the variant.
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.
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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 that 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. Following the proportion of cases without C therefore allowed us to have a good approximation of Omicron cases.», Explains Guillaume Rozier.
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“Broken thermometer“
However, to refine this monitoring, Santé Publique France explained that since December 20, 2021, the screening includes the monitoring of mutations which are specific to the Omicron variant, “like 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 time since the Omicron variant continues to spread at full speed, deplores Guillaume Rozier.
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Public Health France, for its part, assures that the problem should be resolved “quickly», To once again allow reliable monitoring of the evolution of the variant.