“Researchers at the Centers for Disease Control and Prevention are monitoring all emerging variants of the coronavirus, including in 5,700 samples collected in November and December,” according to Jason McDonald, a spokesman for the agency. “To date, neither researchers nor analysts at C.D.C. have seen the emergence of a particular variant in the United States,” he said.
Among the variants circulating in the U.S. are B.1.1.7, first identified in Britain and now driving a surge and overwhelming hospitals there. The variant has been spotted in a handful of states, but the C.D.C. estimates that it accounts for less than 0.5 percent of cases in the country so far.
Another variant circulating at low levels in the U.S., known as B 1.346, contains a deletion that may weaken vaccines’ potency. “But I have seen nothing on increased transmission,” said Michael Worobey, an evolutionary biologist at the University of Arizona who discovered that variant.
That variant has been in the United States for three months and also accounts for fewer than 0.5 percent of cases, so it is unlikely to be more contagious than other variants, according to a C.D.C. scientist who spoke on condition of anonymity because he was not authorized to speak about the matter.
All viruses evolve, and the Coronavirus is no different. “Based on scientific understanding of viruses, it is highly likely there are many variants evolving simultaneously across the globe,” Mr. McDonald, of the C.D.C., said. “However, it could take weeks or months to identify if there is a single variant of the virus that causes Covid-19 fueling the surge in the United States similar to the surge in the United Kingdom.”
Carl Zimmer contributed reporting from New Haven and Noah Weiland from Washington D.C.
