What makes the omicron variant spread so easily?

The omicron variant arrived in the United States around Thanksgiving.Less than a month later, it is the dominant coronavirus strain in the country, and represented 73% of the new infections last week, according to the centers for disease control and prevention (CDC).

How did that happen?Infectious disease experts indicate that there are two key factors that determine the speed with which a virus will spread: the ease with which it is transmitted and the effectiveness with which the organism defenses avoids.

The first investigations suggest that omicron has advantages in both areas.But the data also suggest that the highest transmission rate of the variant has not caused more hospitalizations or deaths.

The preliminary results of a December 14 study led by Alejandro B.Ragon Institute Balazs in Cambridge, Massachusetts, found that this variant was twice more infectious than Delta, and four times more infectious than the original virus.That study, which has not yet been reviewed by pairs, was based on a relatively small sample of 239 patients in Boston and its surroundings, therefore, the results may not be representative of the behavior of an omicron in general.

However, according to DR.David Pride, a specialist in infectious diseases of the UC San Diego, "just looking [the current situation] from the epidemiological point of view, we know that something is very different now".

With so many people not vaccinated, he added, "it was just a matter of time before we saw a mutated version of the virus that was better to infect inoculated people".

It is practically an evolutionary imperative, said Jasmine Plummer, a research scientist at the Cedars-Sinai Medical Center in Los Angeles and who was part of the team that discovered the Epsilon variant of the virus last winter.

"Variants arise because viruses try to survive," said Plummer.“All viruses evolve to evade their guest.So we knew that a joy came ".

And here we are.

Rapid replication

A secret of the omicron success seems to be its ability to replicate quickly.Researchers at Hong Kong University reported that, compared to Delta, an omicron.Its advantage over the original virus is even greater, they added.The difference was apparent just 24 hours after infection.

If that is really the case, it means that people infected with the omicron variant have much more throat viruses waiting to be expelled in the air when they exhale, and especially when they cough or sneeze.He also suggests that they can be infectious before, which would also accelerate the spread of the disease.

A potentially useful signal of Hong Kong's investigation: omicron moved more slowly from the throat to the lungs.In their experiments, the scientists found that the new strain was replicated in the lungs to less than a tenth of the original virus rhythm.That "can suggest less gravity of the disease," according to the university.

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Pride points out that omicron is spreading more easily within homes, suggesting that the virus spreads the air more easily.Another possibility is that a lower amount of the variant to cause an infection is required, he said.

There are many things that we still do not know about how this strain is transmitted, but the CDC expect that "any person with omicron infection can transmit the virus to other individuals, even if they are vaccinated or have no symptoms".

Pride expressed it differently: "We know that this disease is transmitted through people, therefore, the only way to be quite sure that it will not contract it is not to be close to people".

Peak protein

The coronavirus caused by COVID-19 uses a peak-shaped protein on its surface to penetrate healthy cells and use them to produce copies of itself.The available vaccines in the United States cause the creation of antibodies that recognize that peak protein and attack it to destroy the body's immune system.

Omicron has an unprecedented amount of mutations that affect that peak.Balazs and his team counted about three dozen, and their location suggests that they make it difficult for antibodies to recognize a viral omicron particle.That is true regardless of whether the antibodies were generated by a vaccine or prior infection, they wrote.

Researchers from the University of British Columbia in Canada examined the omicron proteins affected by these mutations at the molecular level.They discovered that, together, the changes allowed the peak protein to join the human cells more strongly, compared to the original coronavirus.They published their findings in Biorxiv, a place where scientists seek comments on preliminary work.

Sriram Subramaniam, the main author of the study commented in an interview with the university that even small changes in peak protein "potentially have great implications on how the virus is transmitted, how our body fights it and the effectiveness of treatments".

He added: "Our experiments confirm what we are seeing in the real world: that the pico protein on an omicron is much more effective than other variants to evade immunity produced by both vaccines and natural infection".

Subramaniam pointed out that it was remarkable that the immunity generated by antigens was more effective against the variant, in contrast to the immunity of a prior infection in non -vaccinated patients.It is another signal "that vaccination remains our best defense against an omicron," added.

But that defense may not be very effective without reinforcement.

The study of Balazs found that the protection provided by vaccines or prior infection by Coronavirus was “drastically reduced” against the variant.The only exception was in people who had recently received a dose of antigen reinforcement;They "exhibited a powerful neutralization of omicron," according to the study.

That can help explain why cases of "irruption" and reinfections seem to be rapidly increasing.A South African research team reported December 2 about more than 35.000 Covid-19 reinfections between 2.8 million people who tested positive for the tests during the previous three months.

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