That was the day when, in short order:
Actor-couple Tom Hanks and Rita Wilson announced they had tested positive for the coronavirus, sending a message that everyone was at risk, regardless of their station in life.
Utah Jazz center Rudy Gobert also tested positive, causing the sudden cancellation of one NBA game and quickly prompting the league to suspend its season in recognition of the growing danger to players and fans.
And President Donald Trump announced a ban on most travel from Europe, an indication even he knew it was serious.
By that point, of course, COVID-19 already was a global pandemic. The danger had existed for weeks, if not months, by then.