There’s a deadly virus spreading from state to state. It preys on the most vulnerable, striking the sick and the old without mercy. In just the last few months, it has claimed the lives of at least 39 children.

The virus is influenza, and it poses a far greater threat to Americans than the coronavirus from China that has made headlines around the world.

“When we think about the relative danger of this new coronavirus and influenza, there’s just no comparison,” said William Schaffner, a professor of preventive medicine and health policy at Vanderbilt University Medical Center. “Coronavirus will be a blip on the horizon in comparison. The risk is trivial.”

To be sure, the coronavirus outbreak, which originated last month in the Chinese city of Wuhan, should be taken seriously. The virus can cause pneumonia and is blamed for more than 7,000 illnesses and more than 170 deaths.

The World Health Organization on Thursday declared the outbreak a global emergency requiring a coordinated international response after the number of cases spiked sharply over the last few days. But officials warn much remains unknown.

In the United States, at least six cases of the virus have been reported, including the first case of person-to-person infection. Public health workers are monitoring dozens of additional patients.

And yet, Americans aren’t particularly concerned.

Fewer than half of adults got a flu shot last season, according to the CDC. Even among children, who can be especially vulnerable to respiratory illnesses, only 62% received the vaccine.

If Americans aren’t afraid of the flu, perhaps that’s because they are inured to yearly warnings. For them, the flu is old news. Yet viruses named after foreign places — such as Ebola, Zika, and Wuhan — inspire terror.

“Familiarity breeds indifference,” Schaffner said. “Because it’s new, it’s mysterious, and comes from an exotic place, the coronavirus creates anxiety.”

Some doctors joke that the flu needs to be rebranded.

Measles in the Democratic Republic of the Congo has killed 5,000 people in the last year — more than twice as many as Ebola. Yet UNICEF officials have noted that the measles, which many Americans no longer fear, has gotten little attention. Nearly all the measles victims were children under 5.

The big question, so far unknown, is just how easily the virus is transmitted from an infected person to others. Officials warn much remains unknown, but each patient with the new coronavirus appears to be infecting about two other people.

Coronaviruses can be unpredictable, said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. While some patients never infect anyone else, people who are “super-spreaders” can infect dozens of others.

At Seoul, South Korea’s Samsung Medical Center in 2015, a single emergency-room patient infected 82 people —patients, visitors, and staff — with a coronavirus called MERS, or Middle East Respiratory Syndrome. The hospital partly shut down to control the virus.

“This is one of the finest medical centers in the world, on par with the Cleveland Clinic, and they were brought to their knees,” Osterholm said.

Yet MERS has never posed much of a threat to the United States.