Covid-19: contagiousness, lethality ... Know everything about the different variants

More than a year after its appearance in China, Covid-19 continues to amaze the scientific world, which continues to detect new variants.

The latter raise fears of a more transmissible virus, and therefore more deadly.

What is it really ?

Le Figaro

takes stock.

Read also: Price, conservation, efficacy ... The article to know everything about the different vaccines

What are these new variants?

British, South African, Brazilian, Californian ... Spotted all over the world, some of these variants are already present on French soil.

In its latest epidemiological report dated January 21, Public Health France estimates that 141 confirmed cases of variants have been detected in France.

A number that is probably underestimated.

• The

  "

  British

  "

  variant

Also called VOC202012 / 01, the British variant is the first to have been talked about.

Detected on September 20 in the south-east of England, it has since been identified in 60 different countries.

It would represent, according to the Minister of Health Olivier Véran on January 19, 1 to 2% of confirmed cases in France, or 200 to 300 new cases per day.

A more precise and undoubtedly higher evaluation is long overdue.

In Île-de-France alone, the English variant represents nearly 10% of the cases detected, assured AP-HP doctors on Tuesday, January 26.

Its transmission rate is said to be between 50% and 70% higher than the basic virus.

• The

  "

  South African

  "

  variant

The 501Y.V2 variant became predominant in South Africa, where it emerged last October.

It has since been identified in 23 countries, including France.

According to epidemiologist Salim Abdool Karim, co-chair of the scientific committee at the South African Ministry of Health, this variant "

is 50% more transmissible

".

For the moment, 10 cases have been detected in France, according to Public Health France.

• The

  "

  Brazilian

  "

  variant

The Brazilian variant (P.1) was first detected in January, in Japan, in two children and two adults returning from the South American country.

Few details have leaked out about him, but he is said to be more contagious.

He would then be responsible for the multiplication of cases and the number of deaths in Brazil, especially in the region of Manaus, in the northeast of the country.

France does not know of any case linked to this variant to date, but it has been detected in Germany.

• The

  "

  Californian

  "

  variant

Discovered in mid-January by Cedars-Sinai Medical Center in Los Angeles, this variant, dubbed CAL.20C, "

is

believed to

be partly responsible for the dramatic increase in the number of cases over the past two months

" in California, according to the establishment.

Mentioned for the first time in France by the President of the Scientific Council Jean-François Delfraissy, it is present in more than 30% of contaminations in the City of Angels, one of the most populous cities in the United States.

Are these variants more lethal?

If the data concerning the South African, Brazilian and Californian variants are still scarce, their greater contagiousness makes the scientific world fear a strong resumption of the pandemic.

According to Jean-François Delfraissy, “

the variants are changing the situation

”.

"

If we continue, there will be 12%, 14%, 15% of British variant in the coming weeks

," he estimated on January 25.

More contagiousness means, logically, more deaths.

But the case fatality rate of these variants, and their virulence, still raises questions.

Read also: Covid-19: the Brazilian variant suspected in the new disaster that hits the city of Manaus

In the UK, Prime Minister Boris Johnson explained that the British variant "

may be associated with a higher level of mortality

".

Several British studies, with limited data, actually point in this direction.

"

Unfortunately, it seems that this virus is

" perhaps more deadly, summed up Monday, January 26 at a press conference John Edmunds, of the London School of Hygiene and Tropical Medicine, who estimates at about 30% the additional risk to die linked to the new variant.

“

The situation, alas, is really getting worse.

"

"

Out of 1000 people infected, say sixty years old, ten of them risk dying from the original virus, against 13 or 14 people with the new variant,

" said Boris Johnson's scientific advisor, Patrick Vallance, before tempering these figures by evoking the "

many uncertainties

" that surround them.

They could indeed be linked to the strong hospital tension across the Channel.

"

A third of our patients have been infected with the English variant

(or suspected), nuance Jean-François Timsit, head of the medical and infectious resuscitation service at Bichat hospital, in Paris,

but I did not notice any increased virulence

”

.

Are vaccines effective against these variants?

These new variants are causing fear among experts: will they reduce the effectiveness of vaccines?

For now, Moderna's messenger RNA vaccine is announced to be sufficiently effective against the English and South African variants.

According to preliminary studies, Pfizer's vaccine is also effective against the British variant.

Read also: Will Covid-19 variants make re-infections more frequent?

But several unfinished studies question the immunity induced by a previous contamination, and therefore the effectiveness of the antibodies acquired.

The first analyzes are rather reassuring concerning the English variant: its mutations allow it to penetrate better into our cells, but they do not alter the crucial points of the immune response.

This is unfortunately not the case with the South African and Brazilian variants.

At least one mutation changes the Spike protein, which allows the virus to attach itself to our cells.

It is this protein that the antibodies primarily target.

Initial studies have shown that antibodies from cured patients could be up to 10 times less effective against these variants.

Read also: Covid: will the vaccines be effective against the British and South African variants?

Although current vaccines produce a complete immune response which goes beyond antibodies, by constituting a cellular response in particular, they could however lose some of their effectiveness.

Recall that in 2016, the flu vaccine was less effective due to a mutation.

In the event of a problem, Pfizer assured that it would be able to provide a new vaccine "

in six weeks

".

Why are there variants?

A virus can mutate each time it is transmitted.

It's his way of surviving.

The Covid, like the flu, is no exception to the rule, and has already undergone a large number of mutations since its appearance at the end of 2019.

Read also: The great French mess of the sequencing of coronavirus variants

Covid-19 is an RNA virus, composed of a genetic sequence of 30,000 nucleotides.

It thus opposes DNA viruses, which are less likely to mutate.

When the coronavirus replicates to infect new cells, its genetic makeup is reproduced.

But some copy errors can creep into the new sequence.

As if, in a book containing a total of 30,000 characters, some letters had been modified or deleted during its reproduction.

These errors are mutations.

Most of the time without consequences, they sometimes provide a key advantage for the survival of the virus, including greater transmissibility.

What measures are countries adopting to protect themselves from it?

The emergence of variants has caused a wave of panic to blow over Europe.

In the viewfinder: the United Kingdom and its variant.

Spain

, for example, has banned entry to travelers from across the Channel, except those residing in Spain and Andorra.

Germany

, which does not exclude a closure of its borders, requires a test to people from a risk zone, which includes the United Kingdom ... and

France

.

The latter requires a PCR test from all sources in the Union, except for travelers using land transport.

The

Sweden

banned January 25 for three weeks into its territory from Norway, its neighbor, after the appearance of an English ranging from home near Oslo.

For its part,

Belgium

has announced that it will ban its population from non-essential travel abroad - including within the European Union - from January 27 and for the entire month of February.

Outside Europe, the

Israeli

government

has decreed the suspension until January 31 of international flights.

The

United States

also reinstated restrictions, barring entry to the territory to most non-U.S. Citizens who traveled to Britain, Brazil, South Africa and much of Europe.

To read also: Covid-19: Germany, United Kingdom, Portugal ... Which countries in Europe are reconfining?

In addition to these border measures, fear has given way to tighter national restrictions.

Almost all of the 27 apply at least partial containment.

The

French health authorities

have advised against wearing the category 1 fabric mask and homemade masks, considering them to be too ineffective in the face of the contagiousness of the variants.

In

Bavaria

, the FFP2 mask is required in shops and public transport.

In

Austria

, most closed places are affected by this obligation.