Though the virus seems to be readily transmitted between humans, its apparent death rate of about 2 percent is lower than the 9.6 percent for SARS, and recoveries have risen.

The U.S. has 11 cases, and dozens of people are being tested. Here are the latest updates.

On the ground: Our correspondent in Wuhan reported from a new, 1,000-bed hospital opened from scratch in 10 days (and still partly under construction). In Beijing, empty streets and deserted parks have made for “dystopian vistas.” President Xi Jinping said Monday that the Communist Party was facing a “major test,” while party leaders urged better “propaganda” and “opinion guidance.”

Economic fallout: Chinese stocks plunged on Monday, the first day of trading since the Lunar New Year, and a conservative forecast sees China’s economic growth slipping this year, which will have global repercussions. The Organization of the Petroleum Exporting Countries, and Russia, agreed to meet in Vienna to discuss possibly cutting output to stabilize falling prices. Still, European and American stocks were up.

Related: Hong Kong’s government said Monday that it would close more border checkpoints, as some medical workers went on strike to demand a complete ban on entries from mainland China. And huge complications have confronted Americans seeking to leave China.