British coronavirus variant may soon become predominant in the US by March. Florida being hit hard.

A more contagious variant of the coronavirus first found in Britain is spreading rapidly in the United States, doubling roughly every 10 days, according to a new study.

Analyzing half a million coronavirus tests and hundreds of genomes, a team of researchers predicted that in a month this variant could become predominant in the United States, potentially bringing a surge of new cases and increased risk of death.

The new research offers the first nationwide look at the history of the variant, known as B.1.1.7, since it arrived in the United States in late 2020. Last month, the Centers for Disease Control and Prevention warned that B.1.1.7 could become predominant by March if it behaved the way it did in Britain. The new study confirms that projected path.

“Nothing in this paper is surprising, but people need to see it,” said Kristian Andersen, a co-author of the study and a virologist at the Scripps Research Institute in La Jolla, Calif. “We should probably prepare for this being the predominant lineage in most places in the United States by March.”

Dr. Andersen’s team estimated that the transmission rate of B.1.1.7 in the United States is 30 percent to 40 percent higher than that of more common variants, although those figures may rise as more data comes in, he said. The variant has already been implicated in surges in other countries, including Ireland, Portugal and Jordan.

“There could indeed be a very serious situation developing in a matter of months or weeks,” said Nicholas Davies, an epidemiologist at the London School of Hygiene and Tropical Medicine who was not involved in the study. “These may be early signals warranting urgent investigation by public health authorities.”

Dr. Davies cautioned that U.S. data is patchier than that in Britain and other countries that have national variant monitoring systems. Still, he found results from some parts of the United States especially worrisome. In Florida, where the new study indicates the variant is spreading particularly quickly, Dr. Davies fears that a new surge may hit even sooner than the rest of the country. ...