What Is Coronavirus?

Health officials around the world are racing to gauge the danger posed by a new virus that emerged in central China last month and spread rapidly, sickening hundreds and killing at least six.

Authorities are acting aggressively as the number of cases nearly doubled to 291 over the weekend and stretched to five additional countries, including the first diagnosis in the U.S. The resident of Snohomish, Washington, had recently traveled to Wuhan, China, the epicenter of the outbreak, though he said he hadn’t spent any time at the live-animal market where the virus is believed to have originated and didn’t have contact with anyone who was sick.

People wearing masks arrive at Beijing railway station to head home for the Lunar New Year on Jan. 21.Photographer: Nicolas Asfouri/AFP via Getty Images
As they did during the SARS and Ebola outbreaks, health officials and scientists are tracking patients and testing samples of saliva and other fluids to determine the exact cause and severity of their ailments. They’re identifying and monitoring people with whom the patients were in contact to see if the virus is spreading easily from person to person. And they are placing restrictions on travel to try to limit the exposure to scores of new people.

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The U.S. Centers for Disease Control and Prevention expanded its inspection of airline passengers who had spent time in China to airports in Atlanta and Chicago on Tuesday, building on the 1,200 people who had been screened in California and New York over the weekend. No new cases were uncovered. Six patients in China have died from the infection, which also sickened health-care workers who were caring for them.

“This is an evolving situation,” said Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases. “We do expect additional cases in the United States and globally.”

The World Health Organization will decide Wednesday whether to declare the novel virus an international public health emergency, a designation used for complex epidemics that can cross borders.

“If they declare this a matter of international concern, that will impede commerce and could begin to curtail travel in and out of the country,” said William Schaffner, professor of medicine in infectious diseases at Vanderbilt University School of Medicine in Nashville, Tennessee. “I have a little bit of caution, but I’m not sure we are there yet.”

Researchers at the National Institutes of Health and the CDC are working on a test that will allow doctors to rapidly diagnose the virus in the field, said Schaffner, though Messonnier cautioned that it could take time.