Illustrative image of a PCR test.

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Ludovic MARIN / AFP

  • Almost 44% of positive PCR tests are linked to the British variant in Ile-de-France.

    This should be in the majority at the beginning of March.

  • The South African and Brazilian variants, until then almost non-existent in the region, are progressing in particular in Seine-Saint-Denis.

The Biogroup laboratory had given the alert a few days before Christmas: a first case of the so-called British variant had just been detected in Bagneux, in the Hauts-de-Seine.

Since then, this strain has continued to grow in the region.

The group's 180 Ile-de-France laboratories - which perform nearly half of the Ile-de-France PCR tests - now identify it in nearly half of the positive tests.

And the so dreaded South African and Brazilian variants are beginning to appear.

Interview with Dr Laurent Kbaier, biologist, who centralizes the group's data.

Where is the circulation of the British variant currently in Ile-de-France?

Last week, 44% of positive PCR tests processed by our laboratories were linked to the British variant, compared to 40% the previous week.

We observe a progression of 5 to 10% each week.

At this rate, it is estimated that this variant will take precedence over the original strain by the beginning of March.

There are nevertheless geographical disparities: in Seine-Saint-Denis, it went from 41.8% to 46.7% in one week, while in Val-d'Oise, over the same period, it jumped 34 % to 56%.

However, this strong increase can be explained by the discovery of one or two infectious foci which increase the statistics.

The incidence nevertheless remains relatively stable in the region ...

It's true, and to be honest, it's surprising.

With the progression of the variant, we expected to see an increase in the incidence but for the moment, it is relatively stable or even slightly decreasing.

It is difficult to draw conclusions: is it the effect of the curfew advanced at 6 p.m., of greater respect for barrier gestures or is there a certain inertia before a resumption in the weeks to come up ?

The original strain decreases while the variants increase, it is perhaps this differential which explains this tendency.

It is impossible to express a formal opinion today.

The epidemic has not yet revealed all of its secrets.

Could we infer that the British variant is not as contagious as it is said?

No, because we ourselves see this very strong contagiousness.

With the original strain, it was estimated that about 50-60% of contact cases were positive.

Often, family members were not infected while living with someone who was.

With the British variant, almost all contact cases are positive.

Contrary to what Boris Johnson said, he is not more dangerous, but certainly more contagious.

It is for this reason that it is difficult to predict the evolution of the epidemic ...

What about the South African and Brazilian variants in the region?

The first week of February, they hardly circulated in Ile-de-France, except in Hauts-de-Seine where we had identified 46 cases out of a thousand positive PCRs.

But since last week, the situation has changed: these variants are present even if we are far from the situation facing, for example, the Moselle.

In Paris, we went from 1% of the South African or Brazilian variant to 5.2%, or about 40 cases.

The most worrying situation is in Seine-Saint-Denis where, in one week, we went from 0 to 7.7% of this type of variants: out of 1,300 positive PCR tests, we found 608 British variants and 100 southern variants. -african and brazilian.

What does this portend?

Nothing is inevitable, if contact tracing is effective, the situation can be kept under control.

This remains worrying, however: if we identify 100 cases, we know that there are probably at least twice as many, people who have not been tested or asymptomatic.

We must not forget that during the first wave, Seine-Saint-Denis was particularly affected, it is the department that posted the highest rate of excess mortality, in particular because of the promiscuity of housing and a strong percentage of the population who held so-called essential trades.

We will know a little more in the coming weeks, but the situation should be watched closely.

Why don't you differentiate between the South African and Brazilian variants?

Because there is ultimately little difference between these two variants: they are not more lethal than the original strain but they seem more resistant, especially to vaccines.

This is also the main difference with the British variant.

Why is there no French variant?

To tell the truth, we do not know.

There may already be one, but we don't know.

In France, very little sequencing, that is to say a complete analysis of the RNA of the virus, is done.

We are focusing on finding mutations that we already know.

So since we are not looking for a new variant, it is logical that we do not find one.

The laboratories could however proceed with this sequencing, but for the moment, the government prefers to leave this task to the Pasteur Institute or to the national reference center for respiratory diseases, it's a shame.

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