The U.S. is exercising caution in response to a newly detected variant of the coronavirus called omicron, which the World Health Organization on Friday designated a highly transmissible “variant of concern.” Hours after Friday’s news, the Biden administration announced that starting Monday, the U.S. would restrict travel from South Africa—where researchers first detected omicron—and seven other African countries. (The restrictions won’t apply to U.S. citizens and lawful permanent residents.) “I’ve decided that we’re going to be cautious,” President Joe Biden told reporters on Friday, speaking of the forthcoming ban. “We don’t know a lot about the variant except that it is a great concern and seems to spread rapidly, and I spent about a half-hour this morning with my Covid team led by Dr. [Anthony] Fauci, so that was the decision we made.” 

While omicron cases have not yet been detected in the U.S., Harvard epidemiologist Michael Mina noted that “lack of detection doesn’t mean absence of spread.” Fauci over the weekend said he “would not be surprised” if the new variant had already arrived in America. (New York Gov. Kathy Hochul, declaring a state of emergency on Friday, seemed to share that view.) “We all know when you have a virus that has already gone to multiple countries, inevitably it will be here,” Fauci told ABC’s George Stephanopoulos during an appearance on This Week Sunday. “The question is: Will we be prepared for it?”

Answers about the extent of the new variant’s spread and whether it evades current vaccines “are probably weeks away,” according to the Washington Post. The outlet notes that America’s battle with the highly contagious delta variant this spring—a strain still fueling surges in places such as Michigan and Minnesota— informs the abundance of caution with which the White House is treating omicron. “The delta wave changed everything,” an administration official told the Post, referring to the way the variant upended some progress the U.S. had made in containing COVID-19 this spring. “We have to do everything we can to avoid that [scenario] again,” the official said. 

But besides closing borders, which Fauci described Saturday as a way to buy “some time to really fill in the blanks of what we don’t know right now,” it remains to be seen what other options are available to Biden. “For the time being, health officials are pushing Americans to adhere to existing public health guidelines issued by the CDC and to sign up for Covid-19 booster shots in the coming weeks,” Politico reports, noting “there are currently no other plans to implement other safeguards.”

Given how much remains unknown about the new variant, some experts urged against overreaction as the U.S. and other nations raced to contain omicron’s spread. “Ready, fire, aim is not prudent public health policy,” Scott Gottlieb, the former Food and Drug Administration commissioner, wrote on Twitter. “Bottom line—too soon to know if this will become a dominant strain and if it does, will it be more problematic in terms of vaccine protection,” virologist Susan Weiss told the Post, adding there is “NO evidence that it will cause worse disease.” Fauci himself conceded to the outlet that the administration is taking steps that “may seem somewhat draconian” though he seemed to defend the logic of “blocking the travel from a country that clearly, at this point, is the epicenter” of the variant.

Some experts have questioned whether it is already too late to stop the spread of omicron through travel restrictions, policies that Barcelona Institute of Global Health’s Jeffrey Lazarus said, “give a false sense of security.” The University of Washington’s Nicole Errett noted in an email to the Post that “by the time we have enough information to institute a travel ban, the cat’s already out of the bag, so to speak.” Headlines over the weekend suggested as much, as Australia, Austria, and the Netherlands joined the group of countries with confirmed cases of the variant.

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