The United States' first known case of the new coronavirus variant was discovered in Colorado on Tuesday, according to state health officials.
The variant, called B.1.1.7, has been linked to the United Kingdom. The man who was infected is in his 20s, is isolating and appears to have no travel history, according to Gov. Jared Polis.
That man had been working at an assisted living facility in Elbert County. Health officials suspect, but have yet to confirm, that another man who worked there also came down with the variant, the county's public health director said Wednesday.
California Gov. Gavin Newsom announced Wednesday that the new variant has been found in the southern part of his state.
Here's what we know about the variant:
The new variant came from the UK
The new variant is believed to have originated in southeast England, according to the World Health Organization.
Public Health England says backward tracing, using genetic evidence, suggests the variant emerged in September. It then circulated in very low levels until mid-November.
But scientists did not know whether the mutation originated in southeast England or was introduced there from elsewhere, said Sharon Peacock, professor of public health and microbiology at the University of Cambridge.
Some experts have suggested the new variant could have been amplified because of a superspreader event, meaning the current spike in cases could also have been caused by human behavior.
The new variant spreads more quickly
Health authorities from around the world have said the variant does not appear to be more deadly than previously identified coronavirus strains.
Initial analysis showed that while the variant appears to be more transmissible, there is no evidence it is linked to a higher risk of hospital admission or death, according to Public Health England.
Scientists advising the UK government have estimated the variant could be up to 70% more effective at spreading than others. Peter Horby, chair of the UK's New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG), said last week that scientists were 'confident' the new variant is 'spreading faster than other virus variants.'
Speaking at an emergency meeting of the UK Parliament Science and Technology Committee, Horby explained that the new variant has 'some kind of biological advantage to make it spread faster.'
Scientists still don't have a complete picture as to why, he said, but they are investigating several scenarios.
There is preliminary evidence to suggest the new strain results in a person holding a higher viral load, which means the virus is easier to pass on, Horby said.
Scientist Neil Ferguson, a member of NERVTAG, said the variant may be more infectious for children.
'There is a hint is that (the variant) ... has a higher propensity to infect children,' he said at a news briefing last week organized by the Science Media Centre, though he cautioned that more data was needed. Severe illness due to Covid-19 is still relatively rare for children.
The new variant raises questions about vaccines
There are no signs yet that the current vaccine front-runners won't work against this new variant, experts and drugmakers have said.
The companies behind the first two vaccines to gain authorization in the United States -- Pfizer/BioNTech and Moderna -- are testing their shots to double-check that they're effective against the variant.
The coronavirus has mutated before, and both firms say their vaccines worked against other variations of the virus.
Some US-based scientists have said it's possible the new variant might, to a small extent, undermine the vaccines.
'You could imagine some modest hit to vaccine efficacy, which wouldn't be good, but I don't think it will break the vaccine,' said Trevor Bedford, an associate professor in the vaccine and infectious disease division of the Fred Hutchinson Cancer Research Center.
Adm. Brett Giroir, US Health and Human Services assistant secretary, told 'Fox News Sunday' officials neither have evidence nor do they believe the vaccine would not be effective against the new variant.
'We do believe the vaccine will be effective against this variant,' he said.
New variant likely in US for some time
The United States will likely see 'homegrown variants' of the coronavirus, similar to the one found in Colorado, said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine.
'That variant from the UK was noted in the UK back in September, and it's probably been in the US since September,' Hotez told CNN's Jim Acosta on Tuesday. 'We're going to see homegrown variants that are similar in character in terms of transmissibility, I can almost promise you that.'
Dr. Atul Gawande, a member of the Biden-Harris transition Covid advisory board and a surgeon at Brigham and Women's Hospital, said the variant is almost certainly in several states.
He said the fact that the Colorado man who has the variant didn't travel is a clue.
'An unknown travel history means that this person picked it up the community,' Gawande said. 'Exactly how prevalent it is, is the real question. If it's been spreading, how dominant is it?'
Researchers have scoured genetic sequences of coronavirus in the United States to see if any match up with the UK variant. So far, they haven't found any, but they say that's likely because the US surveillance system isn't catching them.
Fewer than half of 1% of all US coronavirus cases have been sequenced, the Centers for Disease Control and Prevention has said.
At least two dozen countries affected
The variant has already spread globally. As of December 29, at least 26 countries and Hong Kong have reported cases of the new variant.
Aside from the United States, it has also been detected in Denmark, Belgium, the Netherlands and Australia, according to WHO.
Canada has also detected the new variant in Ontario, the province announced Sunday. There are three cases in Ontario, with the latest one in Ottawa.
A similar but separate variant has been identified in South Africa, where scientists say it is spreading quickly along coastal areas of the country.
British health authorities said two cases of the South African variant have been detected in the United Kingdom. The coronavirus variants discovered in the UK and South Africa are both 'more transmissible,' said Susan Hopkins, managing director of Public Health England.
Large swathes of England, including London and the southeast, are now under strict Tier 4 Covid-19 restrictions, and UK government health experts have suggested additional restrictions could be required to beat back this variant.
Dozens of countries across Europe, the Middle East and the Americas have also announced travel bans for the United Kingdom, or new testing and quarantine requirements for UK arrivals.