Photos from 1 year ago show how little the US understood about the pandemic to come

Jaime Jaquez Jr. of the UCLA Bruins celebrates with the crowd after defeating the Arizona Wildcats at Pauley Pavilion in Los Angeles, California on February 29, 2020.Jayne Kamin-Oncea/Getty Images

• A year ago, public-health officials didn't fully understand how the coronavirus spreads.
• Masks weren't yet recommended.
• Photos from early March 2020 show people blowing their noses in public, meeting at bars, and attending college basketball games.

Americans knew little about how their actions were fueling the coronavirus' spread a year ago: People met friends at bars and concerts, blew their noses in public, and gathered en masse for campaign rallies, Mardi Gras celebrations, and college basketball games.

Research now shows the virus was likely spreading in the US as early as December 2019. But even after the US identified its first coronavirus case in January 2020, life continued somewhat normally through mid-March.

The Centers for Disease Control and Prevention didn't recommend against gatherings of 50 or more people until March 15. Had the US instituted broad social-distancing measures one week earlier, a study found, roughly 600,000 infections and 32,000 deaths could have been prevented by May 3.

The following photos, taken roughly a year ago, show how little Americans understood about what was ahead.