How this more contagious virus variant became dominant in the U.S.

The B.1.1.7 strain is spreading among adults and kids, and experts say that's another reason to get vaccinated, fast.

The coronavirus variant known as B.1.1.7, which studies show is both more deadly and more transmissible than the original version of SARS-CoV-2, is now the most common strain circulating in United States, and its growing prevalence has alarmed prominent epidemiologists.

Earlier in the pandemic, not many children were becoming infected with the coronavirus, and they did not appear to be major sources of virus transmission to other age groups. “That changed with B.1.1.7,” says epidemiologist Michael Osterholm, director of the Center for Infectious Disease Research and Policy. “We're now seeing substantial numbers of outbreaks in schools and in school-related activities.”

In a study conducted in the

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