Johns Hopkins University

The United States has reached a sobering milestone while marking the new year. On Friday, the first day of 2021, the U.S. recorded its 20 millionth confirmed coronavirus case since the beginning of the pandemic.

Medical advances have reduced the infection fatality rate in the U.S. But experts warn that indoor gatherings, cold temperatures and pandemic fatigue augur dark months ahead.

The U.S. reported more than 55,000 infections Friday, pushing the total number of cases to more than 7 million. Some two dozen states saw new cases continue to rise this past week.

The number of confirmed coronavirus cases worldwide surpassed 10 million on Sunday while deaths topped half a million. Health officials estimate the actual case count could be much higher.

A small team at Johns Hopkins University early on created what's become one of the most authoritative interactive online dashboards, tracking COVID-19 data around the world.