How new variants of COVID-19 such as omicron emerge and why they raise concern

By Chantal Da Silva and Jon Schuppe -

A new variant of COVID-19 was identified, and called "worrisome," prompting countries to quickly implement new travel restrictions as scientists work to understand the implications of the discovery.

The World Health Organization said on Friday that preliminary evidence

with this variant, compared to other [variants of concern]."

The WHO said there appears to be an increase in cases due to the new strain, called

, in almost every province in South Africa where it was first identified.

He also said that the variant had been detected "in the midst of a faster contagion rate than in previous waves, suggesting that this variant may grow more easily."

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Particles of the SARS-CoV-2 virus, which causes COVID-19, from a patient in the US AP

Here's what we know about how virus strains develop and what makes one "worrisome."

What we know about omicron

The new variant of COVID-19 was first detected in South Africa.

The country's Health Minister Joe Phaahla said scientists were concerned about the high number of mutations and

, the country's most populous province.

In an online press conference on Thursday, Phaahla said South Africa was seeing "an exponential increase" in infections within four to five days and warned that the new variant appeared to be driving that wave of cases. 

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Within days of the variant being identified, several countries said they found cases of B.1.1.529, now called omicron.

Infections have been recorded in Belgium, Hong Kong and Israel, where at least one case was identified in a traveler returning from Malawi, while two other suspected cases were in isolation. 

How are the new variants developed?

As the WHO explains on its website, all viruses, including SARS-CoV-2, the COVID-19 virus, evolve over time.

As a virus replicates or makes copies of itself, it is normal for small changes or "mutations" to occur.

A virus with one or more mutations is considered a variant of the original.

However, when a virus circulates widely in a population, as has been the case with COVD-19, the chances of it mutating increase, explained Dr Deepti Gurdasani, a clinical epidemiologist at Queen Mary University of London.

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Most mutations can have minimal impact on a virus' ability to cause serious infections or health outcomes.

However,

, such as changing the ability of the virus to spread or the severity of the disease it causes, for example, the impact can be significant.

In those cases, Gurdasani said, is when a variant may be on the way to becoming a "variant of concern."

When does a variant become "worrisome"?

According to the definition being developed by the WHO, to be "worrisome" a variant must be associated with one or more

.

Among those changes are an increase in transmissibility, which refers to spread, or an increase in virulence, which means the severity of the disease it can cause.

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"It may also have increased transmissibility compared to other variants or is more capable of escaping vaccines, so it has a property that is different, that changes, or is a change," Gurdasani explained.

"In many ways," he said, omicron "is showing those characteristics."

How concerned should we be about omicron?

As we continue to learn more about the variant, experts say the global community must remain vigilant and cautious. 

"The main concern is that this variant appears to be at least

which is very contagious indeed, and has a large number of mutations in the crucial spike protein, which is where vaccines are targeting," he told NBC. News in an email Bill Hanage, a Harvard epidemiologist.

"This raises concerns that it

" he warned.

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Still, he said, in its current form, "we really have very little data so far on exactly how communicable it is in populations with high vaccination rates, let alone what kind of disease it causes in people with prior immunity."

Jinal Bhiman, senior medical scientist at South Africa's National Institute for Communicable Diseases, said a key area of ​​concern for the country, where there is a relatively low vaccination rate, is that those who have already been infected by the delta variant appear to be returning. to get sick with the new variant.

Bhiman said that suggested that the variant was potentially "evading the immune response that other strains generate."

Still, he noted that the theory was based on initial data, adding that it was

.

“I think the reason the WHO responded the way it did is because of that reinfection vector, that this is the first vector to escape real immunity that could have real implications, but we don't know the severity of this. moment, so it is done as a precaution, ”said Bhiman.

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People wearing masks walk in a shopping mall in Johannesburg, South Africa, Friday, Nov. 26, 2021. Denis Farrell / AP

He also said there are particular concerns about how risky the variant may be in South Africa, given the low immunization rates in the country and limited public health resources to slow the spread. 

While we wait to learn more about the variant, Gurdasani said he doubted omicron would be the last to raise concern in the pandemic.

“

.

There is a large mutational space for this virus, ”he said.

"As long as it replicates, it will mutate," he said.