The US has confirmed its first case of the new, more transmissible coronavirus strain in Colorado

• Colorado officials confirmed the first US case of a new coronavirus variant that was first identified in the UK.
• The strain may be more transmissible than its predecessors, but there’s no reason to think it’s more deadly.
• Public-health experts say the emergence of the new strain is all the more reason to continue wearing masks and social distancing.
• Visit Business Insider’s homepage for more stories.

Roughly two weeks after the UK announced that a new coronavirus strain was likely responsible for an uptick in cases in the south of England, the US confirmed its first case of that same strain.

The infected person, a man in his 20s in Colorado, had no recent history of travel outside the US, the office of Colorado Gov. Jared Polis said in a statement. Local authorities are working to identify any potential chains of transmission while the man isolates.   

UK researchers first detected the new variant three months ago, as a second wave of infections started to mount at the end of the summer. Government leaders have suggested the new variant may be 70% more infectious than its predecessors. Between mid-November and December 9, the variant jumped from being responsible for 28% of London’s new cases to 62%. But there’s no reason to believe it’s more deadly, and experts think existing vaccines will likely still work.

“There is a lot we don’t know about this new COVID-19 variant, but scientists in the United Kingdom are warning the world that it is significantly more contagious,” Gov. Polis said in a statement. “The health and safety of Coloradans is our top priority and we will closely monitor this case, as well as all COVID-19 indicators, very closely. We are working to prevent spread and contain the virus at all levels.”

Countless versions of the coronavirus are circulating, each separated by a handful of tiny changes in its genetic code. The virus typically accumulates two mutations a month, most of which don’t affect its infectiousness or deadliness.

But every so often, “a mutation, or combination of mutations, can arise which confers an advantage to the virus in some way,” Lucy van Dorp, a researcher at University College London’s Genetics Institute, told Business Insider.

That may be the case with the new UK strain, which geneticists have named B.1.1.7. It collected at least 17 mutations at once. Some of the strain’s mutations affect the virus’ spike protein, which it uses to invade cells. That could make it easier for the virus to infect people. Experts believe the strain could have emerged in a patient who was infected for a long time, allowing the virus to mutate in their body, Science magazine reported.

More than a dozen countries have already reported cases of the new strain.

In all likelihood, the variant probably entered the US long before this Colorado case was detected. The US keeps tabs on the genetics of far fewer coronavirus samples than the UK does: Only 51,000 of the 17 million US cases have been genetically sequenced.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told PBS NewsHour last week that he “would not be surprised” if the UK strain was already in the US.

“When we start to look for it, we’re going to find it,” he said.

Public health experts say the new strain’s spread is all the more reason to continue wearing masks and social distancing. 

“Virus mutations can only accumulate if the virus is allowed to be transmitted,” Nathan Grubaugh, an epidemiologist at the Yale School of Medicine, told Business Insider. “So the longer that we allow uncontrolled transmission to occur, the more chances that the virus will have to adapt to human transmission.”