Specialists and health authorities have warned that the most contagious delta mutant, which caused a re-spread of the virus in Britain weeks ago, may lead to a significant increase in the number of cases from this summer if measures are not taken quickly to contain it.

The World Health Organization stated that the Covid epidemic is currently recording a relatively high number of new infections in the world, after it fell to its lowest level since February, and the number of deaths decreased.

But many countries such as Indonesia, Portugal, Russia and Israel are seeing an increase in new cases, at least in part related to the spread of the delta mutant, and other countries fear a similar infection.

And this mutated form of the Corona virus, which was first detected in India, where it spread as of April, is now present in at least 85 countries, according to the World Health Organization, but to varying degrees.

In Europe, it first spread very quickly in the United Kingdom, replacing the alpha mutant that appeared at the end of 2020 in the southeast of England within weeks.

This scenario is expected to be repeated this summer in the rest of the continent, as the European Center for Disease Prevention and Control estimates that this mutation is expected to cause 70% of new infections in the European Union by early August and 90% by the end of the same month.

In the United States, positive cases rose from 10% on June 5 to 35% last week. A similar percentage was recorded in Israel.

This rapid spread is explained by its “competitive advantage” over other strains: this mutant was considered to be 40% to 60% more contagious than the alpha mutant, which in turn was more contagious than the previous strain responsible for the first wave of infections in Europe.

A team of French researchers believes that the rate of transmission of this mutant is between 50% and 80%, according to a study whose results have not yet been published, based on the figures of the Paris region.

The European Center warned against “any relaxation during the summer of the non-medical measures that were applied in early June, which may lead to a rapid and significant increase in the number of daily cases of all age groups.”

This rise will lead to an increase in the number of hospitalized patients and deaths, “which may reach the levels recorded in the fall of 2020 if no additional measures are taken.”

In the United States, the White House scientific advisor, Anthony Fauci, predicted on Tuesday “an outbreak of new cases of the virus,” considering that it is supposed to remain “geographically confined” and less powerful than the previous three waves.

“He poured a bucket of water on the fire to put it out.”

Faced with these risks, the health authorities called on the population to “make greater efforts” in the field of vaccination, as did French Prime Minister Jean Castix on Thursday.

If, according to several studies, the vaccines are less effective against the delta mutant compared to the alpha mutant and the first strain, they retain a high level of efficacy provided the two doses are received.

Depending on the type of vaccine, protection ranges from 92% to 96% in terms of hospitalization risks and 60% to 88% against asymptomatic COVID-19 caused by the delta mutant, according to data from British authorities.

But the prevention of the virus is much lower with a single dose (33% according to a British study).

A European Center document addressed to public opinion revealed that “one dose is not sufficient” to protect against the delta mutant, “and receiving both doses is necessary to protect the weakest groups in society.”

Therefore, the largest number of people receiving the vaccine is necessary but probably not sufficient, as emphasized by epidemiologist Antoine Flahau.

In Britain, “the increase in cases is at the expense of people who have not yet received the vaccine.” He assures AFP that “the minimum required level of vaccination is higher than we initially thought,” adding that given the large number of people who have not yet received the vaccine, especially young people, “the vaccination plan alone is not sufficient.”

The more contagious the virus is, the higher the level of vaccination needed to achieve herd immunity, says Samuel Allison, a biologist who specializes in modeling infectious diseases.

With the mutated Delta, scientists are unanimous in saying that more than 80% of the population must be vaccinated, especially since it is “no longer possible to rely on the natural immunity” of individuals who have contracted Covid-19 because it escapes from it at least partially.

On Wednesday, Andrea Amon, director of the European Center for Disease Control and Prevention, announced that in these circumstances, “and until the protection of the most vulnerable people, we must keep transmission of the Delta mutant to a minimum level by applying strict public health measures that have succeeded in containing the effects of other mutated versions.”

Some countries, such as Israel, announced a return to imposing some restrictions, and Israeli Prime Minister Naftali Bennett justified this by saying, “We want to pour a bucket of water on the fire as long as it is still confined.”