Coronavirus Is Contained in the U.S. Why Are Public Health Officials Worried?

Walling off travelers from mainland China to the U.S. is one thing. Walling off the world is far more difficult.

That’s the challenge facing U.S. health authorities who have adopted a policy of aggressive containment to shield Americans from the new coronavirus. The Trump administration has sharply curtailed travel to and from China, barring most non-citizens who’ve been to China in the past two weeks from entering the U.S. and asking returning Americans to isolate themselves in quarantine.

That strategy has worked for the moment. There are 15 cases of the virus detected and diagnosed in the U.S., with another 45 among Americans repatriated from a virus-infected cruise ship in Japan and the heart of the outbreak in China. But the virus has now spread across six continents in less than a month, meaning it may be impossible to stop.

“Nothing has changed inside our country, but things have changed outside that may ultimately have an impact here,” Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said during a television interview Wednesday.

The coronavirus is firmly established in South Korea, with more than 1,200 cases, including a U.S. soldier stationed there. It’s also spreading in Iran, where 19 people have died. An outbreak has blossomed in northern Italy, threatening to expand in Europe. Japan has at least 164 cases. And on Wednesday, the first South American case was confirmed in Brazil.

President Donald Trump is scheduled to hold a press conference on the U.S. response to the coronavirus Wednesday evening. The administration is likely to impose additional travel restrictions and cancel flights in light of the new outbreaks, a person familiar with the matter said. White House officials are concerned that more stringent restrictions could harm the economy without preventing the virus from spreading in the U.S.

Read more on Bloomberg’s breaking news coverage of the virushere.

Travel restrictions, or the threat of them, can backfire and cause small countries worried about economic shocks to delay reporting cases or minimize outbreaks. That can help an epidemic grow. And travel curbs can create a false sense of security while distracting countries from preparing critical public facilities like hospitals and schools for an epidemic.

Catherine Worsnop, an assistant professor in the School of Public Policy at the University of Maryland, has studied the effects of restrictions on people’s movement in past outbreaks and calls the evidence in favor of them minimal and questionable. At best they can delay an epidemic for a few weeks, and at considerable economic and societal cost, she says.

Government Response

The debate over the threat has resulted in mixed messages from the Trump administration. U.S. health officials have warned of substantial impacts on daily life in the event of an outbreak, while Trump said Wednesday on Twitter that cable news channels were painting an overly dire picture of the situation in order to make him look bad.

More than 4.3 billion passengers around the world traveled somewhere on a plane in 2018, a 6.4% increase from a year earlier, according to the International Civil Aviation Organization, an agency of the United Nations. While Asia and the Pacific account for 35% of that traffic, Europe makes up 26% of the total and the Middle East accounts for almost 10%.

The huge volume of people—vacationing, seeing family, doing business—makes it difficult to contain a pathogen that uses those same people to spread.

“The chances that there will be more importation of the virus into the U.S. has increased in a noteworthy way,” said William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University School of Medicine. “With the virus spreading in those countries, that just means there are more opportunities for the virus—which doesn’t need a passport—to get onto those planes and come to the United States.”

The mild nature of the disease makes it easier to pass undetected, quietly expanding around the world before being noticed when a patient becomes sick enough to be tested and diagnosed. Researchers at Imperial College London estimated on Feb. 21 that two-thirds of coronavirus cases from mainland China remained undetected, potentially resulting in multiple chains of hidden human-to-human transmission.

It was inevitable that this coronavirus would actually spread,” Shruti Gohil, associate medical director of epidemiology and infection prevention at the University of California, Irvine, said in a telephone interview. “Containing it within a single country, no matter how hard China did try, was unrealistic.”


The World Health Organization recommends against travel restrictions to halt the coronavirus. In 2014, researchers at University of Nottingham found that travel restrictions would have only limited effectiveness in preventing spread of influenza, another respiratory virus. Even cutting back air travel by 90% would likely only delay the spread of an epidemic by a few weeks, they found.

“We found no evidence that they would contain influenza within a defined geographical area,” the researchers said of travel restrictions.

Given the similarities between flu and the new coronavirus, a geographical cordon is unlikely to totally stop the latter’s spread. 

“The evidence in favor of their public health benefit now in terms of stopping spread is minimal and they have this added cost of delaying reporting,” said Worsnop, the University of Maryland researcher, in an interview. The potential economic fallout from travel restrictions “can discourage countries from reporting cases and being transparent.”

Travel bans are an easy way for politicians to show they are getting aggressive against a new scourge, her research has found. “Domestic political incentives” drive governments to do it, she says. “This is an easy public thing that governments can do.”

“The public health measures that work are not as reassuring as saying, ‘Hey, I am going to close the border,’” said Worsnop.

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— With assistance by Jennifer Jacobs, and Nick Wadhams

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