TOKYO — China's leader Xi Jinping warned Saturday of an "accelerating spread" of the coronavirus, adding to worries about the scope of a health crisis that has claimed at least 56 lives and triggered emergency health measures in cities across China.

Xi's remarks of a "grave" situation came as China kicked off its traditional New Year's celebrations amid a backdrop of caution and stark measures seeking to contain the virus.

At least 48 million people were ordered on lockdown in central China with a travel ban covering 15 cities in the central Hubei province, where the virus was first encountered. Here's what we know:

●Hong Kong announced that its schools would be closed until Feb. 17 to try to limit the possibility of transmission.

●The Centers for Disease Control and Prevention confirmed that a second person in the United States has been diagnosed with coronavirus.

●Infections have been confirmed in France, South Korea, Japan, Nepal, Thailand, Singapore, Vietnam, Taiwan, Australia and the United States. We’re mapping the spread here.

●Travel bans were extended in central China to put tens of millions of people effectively on local lockdowns. In Wuhan, where the virus was first detected, workers are racing to build a 1,000-bed hospital.

●Authorities around China, including in the capital, Beijing, have canceled the temple fairs and festivals that accompany the Spring Festival to avoid having large public gatherings where the airborne virus could spread.