Home » Technology » Masks, tests, distance… Is Omicron forcing a review of the strategy?

Masks, tests, distance… Is Omicron forcing a review of the strategy?

It was expected, it is now a reality. The Omicron variant is in the majority in France, according to Public Health France. In detail, 62% of tests screened in the last week of the year «showed a compatible profile ” with this variant. This rate was only 15% the previous week, proof of the contagiousness of Omicron. More transmissible, this new version of the virus requires a review of certain barrier gestures and the reliability of the tests.

Less reliable antigen tests

Antigenic tests, which are rapid, have always been less effective in detecting infection with Sars-Cov-2, regardless of the variant. This is due to their functioning, which looks for traces of antigens, outer pieces of the virus, in the nasal passages. Conversely, PCR tests, which amplify the sample to look for the genetic material of the virus, are more reliable.

→ EXPLANATION. Covid-19: recommended for the holidays, are the self-tests reliable?

With Omicron, this distinction has grown even further, pointed out the American authorities at the end of December, without however providing any figures. Normally, all the antigenic tests marketed in France must have an efficiency of at least 80% in the detection of the virus. In fact, it varies greatly depending on the tests, variants and symptoms.

A meta-analysis of 48 studies, published in early 2021, shows a sensitivity ranging from 34% to 88%, with better detection in symptomatic people. In an older synthesis, at the end of 2020, the High Authority for Health showed a large difference, from 17% to 97% of efficiency.

All these studies relate to antigenic tests carried out by health professionals. With self-tests, the risk is even greater because the person can take their sample incorrectly. Note that the risk of a false positive is almost zero: an antigen test may not detect the infection, but if it does detect one, the person is really infected.

PCR tests, on the other hand, remain reliable regardless of the variant and the symptoms. But given the delays and the risk of laboratory congestion, the authorities continue to recommend an antigen test in the first instance. In other words, if your antigen test is negative, but you have symptoms or a high risk of having been exposed, it is better to schedule a PCR in stride.

FFP2 masks that filter better

Barrier gestures are essential. Except that again, the masks seem to be called into question by the Omicron variant. In several European countries, such as Italy or Austria, the authorities now require the wearing of FFP2 masks instead of surgical masks. The latter in fact retain at least 95% of particles of 3 micrometers or more, which serves to protect the others from its own emissions. But carriers are only partially protected, in the sense that only the largest droplets, potentially the most virus-laden, are stopped.

FFP2 masks work in both directions: they protect those around them and the person wearing them. They filter more finely, up to 0.6 micrometers. Not enough to completely stop the smallest aerosols, but much better protection. Provided, of course, to wear it well, which is a challenge, because more filtering, these masks are also more painful to wear for a long time.

Finally, there is the question of the distances to be maintained from one another. If the Omicron variant is more contagious, and antigenic test results have to be weighed against the likelihood of having been infected, how far away should you be concerned? Difficult to provide a definitive answer, because studies are lacking.

→ UNDERSTAND EVERYTHING. Covid-19: how the Omicron variant weakens the vaccine strategy

Postilions and other droplets usually travel less than two meters. But aerosols, the finest particles, can stay in suspension. From where the instruction to ventilate the closed places as often as possible, to evacuate them.


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.