As the omicron coronavirus variant rapidly spreads throughout the world, a study from South Africa suggests the variant is much more likely than other variants to reinfect those who previously had Covid-19.

The omicron variant: The 'good,' 'bad,' and 'ugly' scenarios

Omicron continues to spread, and cases are 'likely to rise'

The omicron variant is continuing to rapidly spread throughout the world, with 246 cases reported in Britain on Sunday—almost double the number of cases reported on Friday. Meanwhile, Denmark confirmed 183 omicron cases, more than triple the number of suspected cases on Friday.

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However, Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, noted that the omicron case count in Britain is still a "tiny fraction" of the roughly 44,000 new coronavirus cases Britain is averaging each day. If by the end of this week omicron represents "even 10% of the delta cases, then I'll be more concerned," Hotez said.

Meanwhile, in the United States, omicron has been detected in at least 17 states. CDC Director Rochelle Walensky said case numbers are "likely to rise."

"What we don't yet know is how transmissible it will be, how well our vaccines will work, whether it will lead to more severe disease," Walensky added. "We're really hopeful that our vaccines will work in a way that even if they don't prevent disease entirely, prevent infection entirely, that they can work to protect severe disease and keep people out of the hospital."

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said it's still unknown how quickly omicron will spread, given the delta variant accounts for 99.9% of all cases in the United States.

"What's going to happen when you have those two competing with each other?" he said, adding, "we have really got to be careful in assessing how severe omicron might end up being."

"We're going to see lots of big numbers over the course of the next several weeks in countries around the world," Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said. "And this shouldn't be a surprise. This virus is just acting like a highly transmissible respiratory virus."

Omicron may be more likely to cause reinfection than other variants

Meanwhile, a study from South Africa suggested the omicron variant is at least three times as likely to cause coronavirus reinfection as other variants.

While the researchers could not directly determine which reinfections were caused by omicron, they did observe a significant spike in reinfections at the time of omicron's emergence. This suggests, they wrote, that omicron "demonstrates substantial population-level evidence for evasion of immunity from prior infection."

"Previous infection used to protect against delta, and now with omicron, it doesn't seem to be the case," Anne von Gottberg, an author on the study from the University of Witwatersrand, said. "We believe that vaccines will still, however, protect against severe disease," von Gottberg added.

Paul Hunter, a professor of medicine at the University of East Anglia, in a written response to the findings, said the study suggests "omicron will be able to overcome natural and probably vaccine-induced immunity to a significant degree." However, just how much "is still unclear though it is doubtful that this will represent complete escape."

Wassila Jassat, a public health specialist at the National Institute for Communicable Diseases in South Africa, said it will take about two to three weeks to determine whether omicron patients will have more severe Covid-19 than those in previous waves.

"Even if we are seeing a slightly less severe disease right now, it's too early to say whether that's a characteristic of this variant, because it's also a nature of the phase of the wave," Jassat said.

Omicron may have evolved in a person co-infected with a common cold virus

Meanwhile, a preliminary study released Friday by the biomedical company Nference suggests the omicron variant may have incorporated genetic material from a common cold virus.

In the study, Nference found that omicron shares similar genetic material to HCoV-229E, a coronavirus that causes the common cold. The researchers suggested its possible omicron formed in a person who was "co-infected" with both HCoV-229E and SARS-CoV-2.

The researchers said both viruses had been discovered in the gastrointestinal and respiratory tissues of co-infected patients, adding that "genomic interplay" between the two viruses could have led to the creation of omicron.

No other variants of SARS-CoV-2 have genetic material similar to HCoV-229E, the researchers said.

(Reyes, Axios, 12/5; Specia/Kwai, New York Times, 12/6; Anthes, New York Times, 12/5; Corder, Associated Press, 12/3; Cheng, Washington Post, 12/3; Chutel/Pérez-Peña, New York Times, 12/2; Steinhauser et. al., Wall Street Journal, 12/2; Steinhauser, Wall Street Journal, 12/3; Dress, The Hill, 12/4)