U.K. variant spreads rapidly in U.S.

Report backs CDC forecast of it being dominant strain in March

The coronavirus variant that shut down much of the United Kingdom is spreading rapidly across the United States, outcompeting other mutant strains and doubling its prevalence among confirmed infections every week and a half, according to new research made public Sunday.

The report, posted on the preprint server MedRxiv and not yet peer-reviewed or published in a journal, comes from a collaboration of many scientists and provides the first hard data to support a forecast issued last month by the Centers for Disease Control and Prevention that showed the United Kingdom variant becoming dominant in the U.S. by late March.

The spread of the variant, officially known as B.1.1.7, and the threat of other mutant strains of the virus, have added urgency to the effort to vaccinate as many people as possible as quickly as possible. The variant is more contagious than earlier forms of the coronavirus and also may be more lethal, although that is far less certain.

The mutations do not change the fundamental way the virus spreads, and masks and social distancing will continue to be effective in limiting infections, disease experts point out.

“Our study shows that the U.S. is on a similar trajectory as other countries where B.1.1.7 rapidly became the dominant SARS-CoV-2 variant, requiring immediate and decisive action to minimize COVID-19 morbidity and mortality,” the authors of the new study wrote.

Florida stands out in the study as the state with the highest estimated prevalence of the variant. The new report estimated the doubling time of B.1.1.7 prevalence in positive test results at 9.1 days.

Florida leads the nation in reported cases involving B.1.1.7, recording 187 infections involving B.1.1.7 as of Thursday, followed by much-more-populous California with 145 infections, according to the CDC.

The new study only looked at data through the end of January, but the percentage of infections in Florida involving B.1.1.7 may have risen from a little less than 5% to approximately 10% in just the past week, Kristian Andersen, an immunologist at Scripps Research Institute and a co-author of the new study, said Sunday in an email.

Mary Jo Trepka, an immunologist at Florida International University, said she is not surprised by the spread of the variant in Florida, because the state has not been strict about mask mandates or other restrictions, and it is a hub for international travel. She worries that the variant will reverse recent favorable trends in infection rates.

“We’re in good shape in terms of numbers of cases coming down, the hospitals are doing well. So is that going to reverse because we’re seeing these variants?” she said. “The message is that we have to work harder to prevent transmission of all these cases of (COVID-19). If we don’t, we’ll potentially see more variants. We need to get everybody vaccinated and we need to do a much better job at preventing transmission.”