(CNN) – Researchers studying the new strain of coronavirus in the United Kingdom think 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 would probably say [esté] in hundreds of people, ”said Michael Worobey, chief of the ecology and evolutionary biology department at the University of Arizona. “It is quite possible that he has been to different places several times.”
Imagine the number of infected travelers leaving London; it’s gone up exponentially, ”said Trevor Bedford, associate professor in the division of Vaccines and Infectious Diseases at Fred Hutchinson Cancer Research Center.
British scientists have traced the earliest known appearance of the new species to September 20 in Kent, a county south-east London.
Worobey and Bedford say they estimate the virus would have reached the United States by mid-November.
Scientists as well as others around the world have traced the genetic sequences of the coronavirus in the United States to see if there is a match with the British variant. They haven’t found one yet, but they say it’s likely because the U.S. surveillance system isn’t detecting them.
Health officials agree.
“You really have to assume it’s already there, and it’s certainly not the dominant strain, but I wouldn’t be at all surprised if it was there,” said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases Tuesday.
“It could be in the United States and we may not have discovered it yet,” Deputy Secretary for Health, Admiral Brett Giroir said Monday.
The new strain of the British coronavirus in the US.
The British variant of the coronavirus has not been identified through sequencing efforts in the United States. According to the Centers for Disease Control and Prevention (CDC) in a scientific report that was published on its website on Tuesday.
However, he says only about 51,000 of the 17 million cases in the United States he counted have been sequenced, less than 0.5%.
“Given the small fraction of sequenced US infections, the variant may already be undetected in the United States,” said the CDC.
To detect new mutations in a virus, samples are collected from infected patients and then subjected to genetic sequencing, looking at the sequence 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.
Since about November 15, when the British 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 United Kingdom, Worobey said.
“We’re flying blind,” said Worobey. “Maybe another equally interesting variant that spreads at a high frequency, but we just don’t see it.”
On its website, the CDC notes that of about 275,000 complete 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 given 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 form of coronavirus
Health officials say research to date shows that the changes seem to make the virus more transmissible, but the variant does not appear to cause more serious illness.
They also say it looks like the vaccine will continue to work against the UK variant at this point. Last month, the CDC launched a pedigree surveillance program where states submit at least 10 samples for testing every two weeks. The agency expects the program to be fully implemented by January.
– CNN’s Michael Nedelman contributed to this report.