"I wouldn't be surprised that it's already here," said Dr. Peter Chin-Hong, an infectious disease professor at UCSF School of Medicine, referring to the new coronavirus variant.
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He says unlike the UK, the United States has not done much genomic testing on positive COVID-19 samples to track emerging variants.
"Mainly because we have so many numbers," said Chin-Hong.
The CDC says out of 17 million positive cases, only 51,000 have been sequenced since the pandemic began. For comparison, the CDC says the UK has sequenced at least 125,000 samples.
"Given the small fraction of US infections that have been sequenced, the variant could already be in the United States without having been detected," says a post on the CDC website.
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Known as the VOC 202012/01 variant, it has become a prominent strain in England.
Given its rapid spread, Chin-Hong says there is speculation that it may be more contagious than the dominant strain in the US, however that hasn't been determined from a biological basis yet.
"We really haven't confirmed it's more transmissible by lab experiments," said Chin-Hong.
He says, the data does show that the variant has not proved to be more deadly. Nor does he believe it will evade protections given by the vaccines that have been developed already.
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"It actually takes years for some virus like COVID to mutate appreciably so that a vaccine wouldn't work," he said.
The CDC has instituted a travel restriction for anyone coming to the United States who has been in the UK in the past 14 days. A negative COVID-19 test taken within 72hours must be presented in order to board an incoming flight. The policy begins Dec. 28.