• December 31, 2019: China reports mysterious pneumonia cases to the World Health Organization.

• January 7, 2020: China says the cases were caused by a new coronavirus.

• January 17: US starts screening for symptoms at certain airports.

• January 21: First US case confirmed in Washington state.

• January 31: US says it will deny entry to foreign nationals who’ve traveled in China in the last 14 days.

• February 6: A person in California’s Santa Clara County dies of coronavirus; link not confirmed until April 21.

• February 17: A second person in California’s Santa Clara County dies of coronavirus; link not confirmed until April 21.

• February 26: CDC announces what’s then thought to be the first possible US case of community spread, in California.

• February 29: A patient dies of coronavirus in Washington state — then believed to be the country’s first novel coronavirus death.