With New York City health officials anticipating the omicron variant to arrive in the coming days, the city’s top doctor on Monday recommended that New Yorkers wear COVID-19 masks "at all times" indoors and in public settings regardless of their vaccination status. 

Appearing alongside outgoing New York City Mayor Bill De Blasio at a Monday news conference, Health Commissioner Dr. Dave Choksi stressed that there are still many unknowns about the new COVID variant first identified last week by researchers in South Africa.  

NYC Health Commissioner Dr. Dave Chokshi at a press conference with NYC Mayor Bill de Blasio. 

NYC Health Commissioner Dr. Dave Chokshi at a press conference with NYC Mayor Bill de Blasio.  (NYC Mayor's Office)

"New York City has one of the strongest variant surveillance systems in the country, sequencing hundreds of cases a week. And we do anticipate detecting omicron in New York in the coming days based on what we know about its global spread," Choksi said. "A lot still is unknown about omicron because it’s so early. But studies are underway, and we will know more about the variant in the coming weeks."

Choksi’s forecast came amid a warning from the World Health Organization that the global risk from the omicron variant is "very high" based on the early evidence. The WHO said the mutated coronavirus could lead to surges with "severe consequences." 

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The assessment from the U.N. health agency, contained in a technical paper issued to member states, amounted to WHO's strongest, most explicit warning yet about the new version. 

President Joe Biden speaks about the COVID-19 variant named omicron, in the Roosevelt Room of the White House on Monday.

President Joe Biden speaks about the COVID-19 variant named omicron, in the Roosevelt Room of the White House on Monday. (AP/Evan Vucci)

Choksi said preliminary evidence suggested that people have been infected with COVID-19 in the past may be more susceptible to being re-infected with omicron. 

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"This underscores our strong recommendation to get vaccinated regardless of whether you have already had COVID-19," Choksi said. 

Choksi expanded on his thoughts in a Twitter thread, saying that the delta variant remains the dominant strain in New York City. 

"Our understanding of omicron will advance, and we’ll be able to adjust our public health strategies accordingly," Choksi said. "Until then, let’s bring to bear our tried-and-true tools that are already helping us keep COVID-19 at bay." 

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Countries around the world, meanwhile, are closing their borders as scientists race to figure out just how dangerous that omicron variant might be. 

People carry shopping bags on Fifth Avenue as the city continues the re-opening efforts following restrictions imposed to slow the spread of coronavirus on December 21, 2020 in New York City. (Photo by Noam Galai/Getty Images)

People carry shopping bags on Fifth Avenue as the city continues the re-opening efforts following restrictions imposed to slow the spread of coronavirus on December 21, 2020 in New York City. (Photo by Noam Galai/Getty Images) (Noam Galai/Getty Images)

The WHO said there are "considerable uncertainties" about the omicron variant. But it said preliminary evidence raises the possibility that the variant has mutations that could help it both evade an immune-system response and boost its ability to spread from one person to another.

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"Depending on these characteristics, there could be future surges of COVID-19, which could have severe consequences, depending on a number of factors, including where surges may take place," it added. "The overall global risk ... is assessed as very high."

The Associated Press contributed to this report