Is this time the right one? Or, while the Omicron variant surprised us twice at the end of last year and in the spring, could the decline in contaminations again be suddenly stopped? Director of the Lyon National Reference Center (where the tests are sequenced), Bruno Lina shares a rather optimistic analysis of the continuation of the pandemic. Still, some worry about less accurate tracking of the outbreak due to the sharp drop in testing performed compared to January. Less concerned about this drop in screening, the professor of virology believes in the hypothesis of a seasonality of the Covid-19 virus. A scenario that will be verified this winter… even if other sub-variants of Omicron emerge in South Africa. Maintenance.
Capital: Do the new BA.4 and BA.5 sub-variants threaten the decline of the second Omicron wave?
Bruno Lina : They are very similar to other Omicron strains. There is therefore no reason for them to upset the epidemic trend. This tends towards a seasonality of the virus, that is to say that Sars-Cov-2 would circulate more each winter like the flu virus. A new variant, which has nothing to do with Omicron, would have to appear to invalidate the scenario of a seasonality of the virus.
Capital: So do you think we’re done with the pandemic? Has the endemic phase started?
Bruno Lina : I hate that word “endemic” because it’s used all over the place and doesn’t mean much. A virus is said to be endemic when it is permanently present in an environment. He has been for some time now. What we hope and what is happening with the two Omicron waves is that we are coming out of the so-called pandemic circulation period. We are heading towards a seasonal circulation of Sars-CoV-2. We don’t have the proof yet, we’ll check it next winter.
Capital: But we are testing a lot less than at the beginning of the year. Isn’t the photograph of the epidemic too vague?
Bruno Lina: This is consistent with the reduction of measures to control the spread of the virus. People are wearing masks less and less and isolation is still recommended but not compulsory*. We are learning to live with the virus. If you have a positive antigen test and symptoms suggestive of Covid-19, you continue to isolate yourself, protect yourself and protect others. Despite everything, we carried out more than 2 million tests last week. Admittedly, we are far from 10 million per week in January, but we are still much more efficient than other European countries. We do not have a perfect vision of the epidemic, but clear enough to calculate declining incidences. We are not blind.
Capital: Unlike other European countries, the tests are free for the majority of French people, as long as they are vaccinated. What will happen when they become chargeable again?
Bruno Lina : It was to properly monitor the evolution of the epidemic that we insisted that the tests remain free. (They are paying for non-vaccinated since October 15, editor’s note). Of course, testing won’t be free forever. If the virus becomes seasonal like other winter diseases, they can easily become chargeable.
Capital: Isn’t the reliability of the tests likely to deteriorate with the new BA.4 and BA.5 variants?
Bruno Lina: This is a legitimate question, asked very regularly since the Alpha variant (from the United Kingdom, editor’s note). But all the PCR tests marketed in France detect all viruses without any problem. As soon as a new strain appears, we monitor daily on the basis of all the sequences, that the tests are able to detect all the variants. This is valid for all Omicron sub-variants, from BA.1 to BA.5.
Capital: How do you explain then, especially during the BA.2 wave, that people had to pass several tests before being detected positive?
Bruno Lina: The reliability of the test will first depend on the sampling technique. There is the PCR, the most unpleasant because it is a nasopharyngeal sample during which the professional uses a swab which penetrates up to 8 cm deep into the nostril. The question is whether it is necessary to use this technique. Because there is also the self-test or the antigen test. In this case, only a nasal swab is taken. The problem is that if, in the same infected individual, you do a PCR and a self-test, the sensitivity will not be the same. On the other hand, we know that the salivary PCR sample, recommended in children, obtains good results, almost similar to the nasopharyngeal.
Capital: Are the latest variants of the coronavirus therefore less well detected by antigens?
Bruno Lina: If you take a nasal swab rather than a nasopharyngeal swab, it is possible that the virus will not be detected. Because this type of test is less sensitive. In particular if you choose to do a self-test in which the sample is taken from a very shallow depth.
Capital: And what about false negatives with Omicron?
Bruno Lina : Antigen tests and self-tests have a specificity that is not 100%. There may be false positives. This is much rarer with PCRs. But the distorted results exist in both directions: there are false negatives as well as false positives. Among antigens, for example, there are between 1 and 2% false positives. The person who has tested positive when they are not may be sick, have respiratory symptoms, but not have contracted Covid-19. She was instead infected with a rhinovirus or an adenovirus. But the reliability of the tests also depends on the quality of the sample.
Capital: How do you know if the direct debit has been made?
Bruno Lina: The ideal sample is already in a person who has blown his nose. If you have a full nose, the swab will pick up mucus. It is therefore necessary to hunt this mucus, in order to discover the viral cells. The person must not move from the start of the test. If the swab draws from a depth of only 3 or 4 centimeters, the result may be distorted. On the other hand, if the sampler manages to get the swab 8 centimeters deep into the nostril, even if you move a little, the result is reliable. Above all, we recommend keeping your head straight and rotating the swab in the nostril. Like a key in a lock.
* Isolation is no longer mandatory for contact cases but remains imposed on positive people: the duration is 7 days if you are fully vaccinated or if you are under 12 years old. It can be reduced to 5 days in the event of a negative test (antigen or PCR). Isolation is extended to 10 days for non-vaccinated or partially vaccinated. It can be reduced to 7 days in the event of a negative test. Since March 21, positive antigen tests must again be confirmed by PCR.
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