It's been three years since the first Covid-19 case in the United States. What have we learned and what more do we need to understand?

It's been three years since the first Covid-19 case was diagnosed in the United States, on January 20, 2020. In the time since, nearly 1.1 million Americans have died from the coronavirus; the US has reported 102 million Covid cases, more than any other country, according to Johns Hopkins University. Both figures, many health officials believe, are likely to have been undercounted.