The parallel was tempting. The marked increase on Wednesday in the number of cases of the new coronavirus detected in France reached nearly 1,700 contaminations in 24 hours. This is a level that has not been known since May 30, as many media quickly pointed out.
What can you imagine a circulation of the virus as important as three months ago? Not so fast. The way health authorities monitor the epidemic in particular has been revolutionized in the meantime. Enough to render null and void any comparison between the two periods ...
"What must be understood is that these figures come from two very different contexts in terms of testing," points out Antoine Flahault, director of the Institute for Global Health at the University of Geneva.
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At the end of May, the tests primarily concerned patients admitted to hospital. Other patients, with less alarming symptoms, were sent home without even being diagnosed. "In reality, we had a very imperfect view of the circulation of the virus," notes the epidemiologist.
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Since then, the authorities have implemented a much more proactive screening policy. Of the 3.5 million tests carried out in France since the start of the epidemic, 2.5 million have been carried out in June and July.
9 out of 10 cases not detected
The “contact tracing” process, which consists of testing any person who has been in contact with a patient, leads in particular to the detection of many asymptomatic cases, as may also be allowed by certain tests carried out preventively, for example before a surgical operation or of a trip.
So many patients who would have passed under the radar of health authorities in May. In the canton of Geneva, studies have shown that "nearly nine out of 10" had not been detected at the height of the crisis. "For France, it is likely that the figures for May will have to be multiplied by five or by 10 to know the real number of cases at the time", calculates the researcher.
The effects of this new policy are also found in other indicators. “While the tests mainly concerned the most serious cases during the first wave, it was noted that nearly 20% of the identified patients died,” emphasizes Antoine Flahault. Today, with the multiplication of tests, that figure has fallen to 2.5%. "
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The daily figures for hospitalizations and admissions in intensive care, significantly higher at the end of May than today, remind us that the epidemic does not seem to have returned to its level of three months ago.
On May 30, there were 227 hospital admissions, against 137 on Wednesday, and 29 in the departments reserved for the most serious cases, almost twice as many as the 15 on Wednesday. “At the time, we were in a phase of recession, resides Antoine Flahault. Currently, we are at low tide, although the virus is present. The photography is just a lot sharper than before. Hence, logically, a tendency to overinterpret the slightest movement.
