Every day, Le Parisien takes action to answer your questions about the coronavirus. We are interested today in the questioning of Meghzouli who wonders what is the number of people tested negative at Covid-19.
According to the latest epidemiological bulletin from Santé Publique France dated April 2, 195,408 tests by nasal swab (so-called PCR tests) were analyzed in the hospital laboratory between February 24 and March 27. 45,967 of them gave a positive result to Covid-19, or 23.5%.
In addition, medical biology laboratories outside hospitals analyzed 28,846 tests as of March 31, of which 8,660 were positive.
75.5% negative test
In total, more than three quarters of the tests (75.5%) whose results are already known have therefore been negative since the start of the epidemic. This may seem like a lot, since only patients with severe symptoms in France could be screened during the first weeks.
But there are several reasons for this. On the one hand, part of the symptoms are common to other diseases. Fever, cough or sore throat can also occur when you have the flu or a cold but not Covid-19, for example.
On the other hand, it can happen that an infected patient is "false negative", that is to say that the test does not detect the disease. It is estimated that this happens about two in five. Some people are tested several times to make sure they don't miss a positive result.
“Rise in power” of screening
Finally, "patients with signs of Covid-19 are no longer systematically classified and confirmed by biological test", indicates Public Health France. Some people who are strongly suspected to be sick do not count positive tests. This is particularly the case for those who do not have co-morbidities. Conversely, symptomatic health professionals are much more systematically screened.
The authorities have gradually announced, since the end of March, their desire to "step up" on screening. While increasing the number of PCR tests, five million rapid tests were ordered. "They will allow us to increase our screening capacity in the order of 30,000 additional tests per day in April, 60,000 in May and more than 100,000 in June", specifies the Management General of Health.
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