More than 42,600 people have a rapidly spreading disease known as Coronavirus, which causes pneumonia and has killed more than 1,000 -- nearly all in China, where it began two months ago. The U.S. government warns Americans not to go there and says those visiting or working in China should consider leaving. State Department diplomats and their families were flown home in late January. Three airlines – Delta, United and American – suspended trips to China, where the disease has reached every province. U.S.-bound flights from that Asian country must use one of seven airports where passengers and crew get health screenings. Anyone who has been in the city of Wuhan or its province faces a mandatory two-week quarantine (isolation) at a federal site.

The extraordinary steps are in place because there's no vaccine yet for the contagious new virus, which the World Health Organization says is a global public health emergency. Chinese doctors in Wuhan (WOO-hahn), a major metropolitan area, saw the first infected patients in early December. The government didn't quarantine the city, preventing departures, until Jan. 23. By then, according to the mayor, five million people had already fled.

The disease came from animals, as is common with new and troubling viruses. Ebola and flu are other examples. As part of its response, China has closed schools and shut live animal markets. Though Coronavirus poses a medical mystery, it’s not at a level of some more common health threats. Flu, for instance, has killed at least 8,200 people in the United States so far this 2019-20 season. Still, as the Trump administration's secretary of health and human services says: "We don't yet know everything we need to know about this virus."

U.S. official says: "Americans should know that this is a potentially very serious public health threat, but, at this point, Americans should not worry for their own safety." – Secretary Alex Azar, Department of Health and Human Services

Columnist says: "China informed the World Health Organization of the virus on Dec. 31, but kept its own citizens in the dark." – Nicholas Kristof, New York Times

Congresswoman says: "There's a lot of mistruths, fear-mongering and bad advice out there on the Coronavirus. Like the virus itself, measures must be taken to limit the spread of misinformation. Social media companies must be held accountable and help prevent this." – Rep. Debbie Dingell, D-Mich.