A coronavirus variant first identified in Britain is rapidly spreading in the United States, threatening to bring a surge of new cases as its prevalence doubles roughly every 10 days, according to a new study. The paper was posted online on Sunday and has not yet been peer reviewed, but it does offer the most comprehensive look at the rise of B.1.1.7 in the country hit hardest by the pandemic. A team of scientists led by researchers at The Scripps Research Institute analysed half a million test samples collected across the country since last summer. Rather than individually sequence all of them, they were able to identify a particular anomaly that was a “reliable proxy” for B.1.1.7. They also analysed the full genetic sequence, a more time-consuming process, for 212 samples. They found the variant was introduced at multiple points into the US in November 2020, and while currently low in overall frequency, it is set to become the dominant form of the virus by March. The team added that transmission rate was at least 35-45 per cent higher than more common variants, and its prevalence is doubling every week and a half. WHO backs AstraZeneca vaccine after South Africa delays jabs Britain saw devastating waves of Covid after B.1.1.7 became dominant there, and the variant has been observed in many European countries including Portugal and Ireland. “B.1.1.7 is much more contagious – so it can quickly overwhelm a nation,” Ashish Jha, dean of the Brown University School of Public Health, tweeted in response to the paper. Ireland had got its outbreak under control by late 2020, but in January B.1.1.7 triggered an exponential wave there that it is now recovering from. The United States has had the world’s largest outbreak, with more than 27 million confirmed cases and 463,000 deaths, but its last wave peaked around January 8 and infections have been dropping since. No other country has recorded even half that number. India, with more than 10.8 million confirmed cases, has the second most. There have been more than 106 million confirmed cases of the virus worldwide. There has been a decline in confirmed cases this month in the US, which averaged about 118,000 new positive tests over the last week, according to New York Times data. That average was about 31 per-cent higher two weeks earlier. There are fears that B.1.1.7 could trigger a new spike, and it is spreading particularly rapidly in Florida, according to the study. US Republican congressman Ron Wright dies after coronavirus battle The study’s authors called for the United States to build up its Covid genomic surveillance system. “I’m asking everyone to please keep your guard up,” Rochelle Walensky, director of the Centres for Disease Control and Prevention (CDC) said at a briefing on Monday. “The continued proliferation of variants remains of great concern and is a threat that could reverse the recent trend positive trends we are seeing.” Current vaccines remain effective against the variant, while the use of masks drastically reduces transmission. There is, however, concern about diminished effectiveness of the current vaccines against a strain first identified in South Africa. Dr Anthony Fauci, the US government’s top infectious-diseases expert, said delaying the second dose for too long on a widespread scale could actually invite more problematic mutants to arise. “We feel the optimum approach would be to continue with getting as many people on their first dose as possible, but also making sure that people – on time – get their second dose,” Fauci said. US President Joe Biden, who took office last month, said his predecessor Donald Trump’s handling of the pandemic “was even more dire than we thought”, in an interview with CBS News Sunday. There was less vaccine available than they had initially been led to believe, he said. Agence France-Presse and Tribune News Service