Covid-19: what do we know about the two new variants that are worrying? - France 24

Paris (AFP)

The emergence in the United Kingdom and South Africa of two new variants of Sars-CoV-2, more contagious according to the first data, is of great concern to the international community.

Update on these two changes.

- What are these variants?

All viruses mutate.

These mutations are changes that occur when they replicate.

Scientists have observed multiple mutations in Sars-CoV-2 since its onset, the vast majority of which are harmless, but some may give it an advantage for its survival, including greater transmissibility.

Detected in November in the UK, the B.1.1.7 variant, now called VOC 202012/01, "probably" originated in the south-east of England in September, according to Imperial College London.

It quickly spread throughout the UK and has now been detected in dozens of countries around the world, from the United States to South Korea, including India, France and Denmark.

Most of these cases are linked to the United Kingdom, but for a few, no link with this country could be traced, which proves that this variant has already established itself locally.

This is what is happening in Denmark, one of the countries with the most samples, where 86 cases have been identified (with an increasing frequency).

Another variant, called 501.V2, is now the majority in South Africa.

It was detected in samples dating back to October and then spotted in a few other countries around the world, including the UK and France.

For both variants, the cases are probably underestimated, experts say.

These two variants present several mutations, one of which, called N501Y, is the center of attention.

It is located on the coronavirus spike protein, a spike on its surface that allows it to attach to the ACE2 receptor in human cells in order to penetrate them and thus plays a key role in viral infection.

This N501Y mutation is known to increase the ability of the virus to attach to the ACE2 receptor.

"There is no clearly established relationship between attachment to ACE2 and increased transmissibility, but it is plausible that such a relationship exists," says the European Center for Disease Prevention and Control (ECDC) .

- No longer transmissible?

Several scientific studies, not yet peer-reviewed and based mainly on modeling, conclude that the British variant is much more transmissible.

This confirms the initial assessments of the group of researchers NERVTAG which advises the British government, which estimated that transmission is increased by 50 to 70%.

Thus, according to calculations by the London School of Hygiene and Tropical Medicine (LSHTM), the British variant is 50 to 74% more contagious.

For their latest report, released Thursday, researchers at Imperial College London analyzed thousands of Sars-CoV-2 virus genomes sequenced between October and December.

According to two different methods, they conclude that this variant has a "significant advantage" in terms of contagiousness: 50 to 75% more contagious, or a reproduction rate of the virus (R) between 0.4 and 0.7 higher than the virus. usual.

Preliminary results for the South African variant also indicate higher transmissibility, but less data are available.

However, some experts believe that there is not enough data to assess with certainty the contagiousness of the two variants.

"We must remain cautious. The result in terms of incidence is a combination of factors that combines the characteristics of the virus but also the prevention and control measures put in place" (distancing, wearing a mask, closing of establishments open to the public ...), Bruno Coignard, director of infectious diseases at the French health agency Santé Publique France, told AFP.

- More problematic?

"There is no information that infections with these strains are more serious," notes the ECDC.

But the risk "in terms of hospitalizations and deaths is high".

"Whoever says higher transmissibility possibly means a much higher incidence, and therefore even at equal lethality, greater pressure on the health system", continues Bruno Coignard.

A variant of Sars-CoV-2 "50% more transmissible would pose a much greater problem than a variant 50% more lethal," insists on Twitter the British epidemiologist Adam Kucharski, supporting statistical evidence.

With a reproduction rate of 1.1, a mortality rate of 0.8%, and 10,000 people infected, we would end up with 129 deaths after a month, he explains.

If the death rate is increased by 50%, the number of deaths would reach 193. But if the rate of transmissibility increased by 50%, 978 deaths would be deplored.

The impact would be particularly noticeable in countries where even a small increase in transmissibility would push the reproduction rate above 1, accelerating the epidemic.

The British variant is "really the concern of the moment" because "it can precipitate us into an extremely complex situation", warned on Franceinfo radio on Monday the epidemiologist Arnaud Fontanet, member of the Scientific Council which guides the French government .

In addition, the first studies on the British variant also show a greater contamination of young people under the age of 20, which raises the question of whether or not schools are open.

Thus, the LSHTM study believes that restrictive measures such as containment in place in the UK in November would not be effective enough to control the outbreak, "unless schools, colleges and universities are also closed ".

- How effective are vaccines?

While the vaccination campaigns that have just started offer hope for a way out of this global health crisis, some question the ability of vaccines to fight against the new variants.

For the two variants, "there is at this stage not enough information available to estimate (if they pose) a risk on the effectiveness of the vaccines", estimates the ECDC.

However, "with the current state of our knowledge, experts believe that current vaccines will be effective against these strains," said Henry Walke of the US Centers for Disease Prevention and Control (CDC) in a statement. press conference Wednesday.

The German laboratory BioNTech, originally with Pfizer of the world's first authorized Covid-19 vaccine, assured him that it was able, if necessary, to provide a new vaccine "in six weeks" to respond to a mutation.

- How to fight?

It is “illusory” to think that we can eradicate or completely prevent the spread of new variants, believes Bruno Coignard, noting that the objective is to “delay as much as possible” their dissemination.

Thus, for countries where cases of new variants are not widespread, the ECDC recommends "efforts to slow the spread, similar to those put in place at the start of the epidemic": testing of people arriving from areas to risk with possible quarantines, isolation and tracing of reinforced contacts for infected people, limitation of travel ...

It also calls for monitoring the incidence of these variants, in particular by increasing the number of virus sequencing.

Some PCR tests can also give an indication of the presence of the British variant, in order to then better target the sequencing, explained Professor Fontanet, according to whom "extremely aggressive monitoring" is essential.

At the individual level, "because these variants seem to spread more easily, we must be even more vigilant in our preventive measures to slow the spread of Covid-19", insisted Dr. Walke, referring to the wearing of the mask, to physical distancing, hand washing and ventilation of closed spaces, without forgetting to avoid crowds.

© 2021 AFP