Variant of covid-19 would have arrived in the US in November 0:30
(CNN) -
Researchers studying the new strain of coronavirus in the United Kingdom believe it likely arrived in the United States in mid-November and that many people in the United States may already be infected.
"If I had to guess, I'd say [it's] probably in hundreds of people now," said Michael Worobey, head of the Department of Ecology and Evolutionary Biology at the University of Arizona.
"It is very possible that he has come several times to various places."
Imagine the number of infected travelers leaving London;
It has increased exponentially, ”said Trevor Bedford, associate professor in the Division of Vaccines and Infectious Diseases at the Fred Hutchinson Cancer Research Center.
British scientists have traced the earliest known appearance of the new strain to September 20 in Kent, a county southeast of London.
Worobey and Bedford say they estimate the virus would have reached the United States in mid-November.
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Both scientists, as well as others around the world, have tracked down the genetic sequences of the coronavirus in the United States to see if any match the UK variant.
They haven't found any so far, but they say it's probably because the US surveillance system isn't detecting them.
Health officials agree.
"You really have to assume it's already here, and it's certainly not the dominant strain, but I wouldn't be at all surprised if it was already here," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said Tuesday.
"It could be in the United States and we may not have detected it yet," Assistant Secretary for Health Admiral Brett Giroir said Monday.
The new strain of the UK coronavirus in the US
The UK variant of the coronavirus has not been identified through sequencing efforts in the United States.
This according to the Centers for Disease Control and Prevention (CDC) in a scientific report published on its website on Tuesday.
However, he says, only about 51,000 of the 17 million cases in the United States that he has counted have been sequenced, less than 0.5%.
"Given the small fraction of US infections that have been sequenced, the variant may already be in the United States undetected," the CDC said.
To detect new mutations of a virus, samples are collected from infected patients and then subjected to genetic sequencing, looking at the order of the letters in their genetic code in search of something new.
In the United States, only a relatively small number of samples go through this process.
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Since about November 15, around the time the UK variant could have reached the United States, genetic sequencing of viruses found has been done in about 300 people in that country and about 9,000 in the UK, Worobey said.
"We fly blind," said Worobey.
"Maybe some other equally interesting variant is spreading with high frequency, but we're just not seeing it."
On its website, the CDC notes that of approximately 275,000 whole genome sequences in public databases, 51,000 are from the United States and 125,000 are from the United Kingdom.
This difference is especially striking considering the number of most confirmed infections in the United States - more than 18 million - compared to more than 2.1 million in the United Kingdom.
The new strain of coronavirus
Health officials say research so far shows that the changes appear to make the virus more communicable, but the variant does not appear to cause more serious illness.
They also say that at this point, it appears the vaccine will continue to work against the UK variant.
Last month, the CDC launched a strain surveillance program where states will submit at least 10 samples every two weeks for testing.
The agency expects to have the program fully implemented in January.
- CNN's Michael Nedelman contributed to this report.
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