A New COVID-19 Variant Has Hit the US. Here's What You Need to Know.

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A new variant of COVID-19—believed to be more contagious than previous strains—has cropped up in Colorado and California, kicking off new questions about the future of the coronavirus pandemic in the U.S. 

The first known case of the variant, called B.1.1.7, in the U.S. was confirmed in a man in his 20s currently recovering in isolation in Elbert County, Colorado, officials announced Tuesday. The man, a member of the Colorado National Guard, had deployed to a nursing home experiencing a COVID-19 outbreak, the Associated Press reported. The state is already investigating a second suspected case in another of its National Guardsman who was at the same assisted living facility, but results could take up to a week. He’ll remain in isolation until then.

Another case of the COVID-19 variant, which is believed to have originated in the U.K. in September, was found in Southern California, Gov. Gavin Newsom announced Wednesday afternoon, though he did not give further details. 

The COVID-19 variant is not believed to cause more-severe illness or be more deadly, but it appears to “spread more easily and quickly” than others, according to the CDC. The variant has emerged in several other countries, including Canada, Japan, Spain, Switzerland, and Sweden, according to the BBC. 

The first Guardsman in Colorado with the confirmed infection hadn’t been traveling, prompting concerns that the variant has been spreading in the U.S. undetected. 

It’s not exactly clear what makes it more contagious, but if the new variant—one of several currently cropping up around the world—triggers more cases in the U.S., it could burden hospitals already overwhelmed with patients, CDC officials said Wednesday, according to CNBC. Still, experts believe the existing COVID-19 vaccines will be effective against the variant. 

The U.S. now requires that air travelers test negative no more than 72 hours before they depart the U.K. for the U.S. Japan has taken more drastic measures and temporarily banned travel from nonresident foreign nationals after cases involving the new COVID strain were confirmed from people who had traveled to the U.K. 

The U.S. has already struggled to rein in the pandemic, especially since some state and local governments have resisted mask mandates and stay-at-home orders. Millions of Americans have traveled over the holiday season, risking yet another tide of infections despite warnings from health officials. The virus, which has killed more than 330,000 people and resulted in more than 19 million infections nationwide, continues to devastate parts of the country, especially Los Angeles and Southern California.

Scientists believe that the B.1.1.7 strain has gone through 17 mutations, according to Science Magazine. In particular, the spike protein part of the virus, which plays a role in how COVID enters human cells, has undergone changes. 

A preliminary, non-peer-reviewed mathematical model from the London School of Hygiene and Tropical Medicine estimates that B.1.1.7 is 56 percent more likely to be transmitted than previous strains. 

Preliminary evidence also suggests the variant may cause a person to carry a higher viral load, which could cause it to spread more easily, Peter Horby, chair of the U.K.'s New and Emerging Respiratory Virus Threats Advisory Group, said last week, according to CNN. 

The CDC created a National SARS-CoV-2 Strain Surveillance (NS3) program in November to track variations of coronavirus like the one seen in Colorado. The agency said that the program will be “fully implemented” in January. 

The COVID strain discovered in Colorado and California this week can be traced to a strain believed to have “emerged” in the U.K. in September, according to the CDC. That strain spread in London and southeast England in particular and prompted stricter lockdown measures in those areas in December. 

“By chance alone, viral variants often emerge or disappear, and that may be the case here,” the CDC wrote about the new viral strain. “Alternatively, it may be emerging because it is better fit to spread in humans. This rapid change from being a rare strain to becoming a common strain has concerned scientists in the U.K., who are urgently evaluating the characteristics of the variant strain and of the illness that it causes.

It’s possible that the variant was first identified in the U.K. because Britain has the largest coronavirus genome-sequencing system, according to the New York Times.

Experts believe COVID-19 vaccines should work even on variants of the virus, according to the Associated Press, although that still needs to be confirmed. Pfizer and Moderna are both testing their respective vaccines to ensure they protect against the variant found in the U.K., according to CNN. The chief executive of BioNTech, which developed the vaccine with Pfizer, said last week that it’s “highly likely that the immune response by this vaccine also can deal with the new virus variants.”

But the rollout of the vaccine in the U.S. has also been slow and haphazard. Of the 14 million doses sent out this month, only 2.6 million have been administered to healthcare workers and nursing home residents, according to NBC News.