美国国家公共电台 NPR New Coronavirus Sparks More Aggressive Global Response Than（在线收听）

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There are as many as 5 million severe cases of the flu each year. So far, there have been around 20,000 cases of the new coronavirus, most of them mild. Yet, in response to the coronavirus, governments have shut down border crossings, airlines have canceled flights. The U.S. is quarantining travelers from Hubei province in China. NPR's Nurith Aizenman reports on why the response has been so aggressive.

NURITH AIZENMAN, BYLINE: A major factor is the uncertainty surrounding this new virus. Contrast that with seasonal flu.

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ANTHONY FAUCI: There's a certainty of seasonal flu. I can tell you all guaranteed that as we get into March and April, the flu cases are going to go down.

AIZENMAN: Anthony Fauci directs the U.S. National Institute of Allergy and Infectious Diseases.

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FAUCI: You could predict pretty accurately what the range of the mortality is and the hospitalizations.

AIZENMAN: But health officials don't know how deadly this new virus is. For instance, right now, it does seem to be more of a killer than the flu. Christian Althaus is a computational epidemiologist at the University of Bern, Switzerland.

CHRISTIAN ALTHAUS: For a flu, one can roughly say that maybe 1 in 1,000 or less of infected people dies. But for this new coronavirus, it could well be about 1%.

AIZENMAN: In other words, a death rate that's about 10 times greater than the flu. But even if the death rate ultimately turns out to be more on par with the flu, Althaus says there's another consideration here. If we could permanently eliminate the flu, we would. Unfortunately, the flu is already too widespread. This new coronavirus has only just started circulating in humans.

ALTHAUS: Now we have, basically, the opportunity to prevent spread of a new respiratory disease in the first place.

AIZENMAN: But with at least 17,000 confirmed cases, is it still possible to stamp out this disease? Althaus notes that nearly 20 years ago, the world did succeed in eliminating another coronavirus; the one that caused severe acute respiratory syndrome, or SARS, which infected at least 8,000 people globally. But here's the thing. With SARS...

ALTHAUS: The majority of infected individuals do not transmit the infection at all.

AIZENMAN: A lot of people who were infected didn't pass SARS on, says Althaus. Instead, the disease mostly spread through what's known as superspreading events - rare cases of people who shed an unusual amount of the virus or hospitals that had terrible infection control such that a lot of health workers got sick and then passed the disease on further.

ALTHAUS: A small fraction of infected individuals can infect a lot of additional people, like 10, 20 or 30 people.

AIZENMAN: And as scary as that sounds, this pattern of spread is actually easier to contain. With SARS, officials were able to put most of their energy on identifying the superspreading sources.

ALTHAUS: If you miss a few infected individuals, it might not be that bad because they might not cause a new transmission chain anyway.

AIZENMAN: Unfortunately, Althaus and others have been modeling this new coronavirus, and their work suggests that it may be spreading at a much more steady rate, a lot like the flu.

ALTHAUS: That means that we have to be very careful that we really find all individuals that are infected with this virus that travel to other countries.

AIZENMAN: The U.S. has taken the aggressive step of putting into quarantine travelers from the province in China with the most infections. Dr. Nancy Messonnier is with the U.S. Centers for Disease Control and Prevention.

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NANCY MESSONNIER: The goal here is to slow the entry of this virus into the United States.

AIZENMAN: And stop it before it can take root and become another seasonal disease - but it may be too late. The latest estimates suggest that there could be tens of thousands more infections in China that have not yet been diagnosed.

Nurith Aizenman, NPR News.

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