STEVE INSKEEP, HOST:
How severe is the spread of the coronavirus? Health officials around the world are plainly concerned. An outbreak centers on China where officials have blocked traffic in and out of multiple cities. Hong Kong cut back connections with the mainland. The United States is urging Americans to avoid all nonessential travel to China. NPR science correspondent Richard Harris is here to assess what officials are up against. Richard, good morning.
RICHARD HARRIS, BYLINE: Good morning, Steve.
INSKEEP: What are some numbers that give us a sense of the scale of this?
HARRIS: Well, the numbers keep growing rapidly, but the latest figures show about 4,000 cases now - the vast majority in China - and more than a hundred deaths have now been reported. Those are probably even underestimates. And at least a case or two has been reported in at least 16 other countries around the world. Just five cases here in the United States have been diagnosed. And those are all among people who had recently been in the city of Wuhan where the outbreak began late last year.
INSKEEP: You said just five cases in the United States. Is there a risk of more?
HARRIS: There are likely to be more cases, health officials say, especially from other people who had been in China and have come home recently. So less clear is whether any of the people who have it now have passed it along to others. It's a respiratory virus, so it could spread from a cough or a sneeze or perhaps from a surface, like a bed rail in a hospital room or something. And people at greatest risk would be the actual health care workers who were in those rooms and caring for those patients.
INSKEEP: How deadly is this virus if you get it?
HARRIS: That is an unresolved question. But according to reports in the latest journal, The Lancet, it seems like only 3% thus far in China who came down with the disease actually died. But that 3% number is subject to change. As more deaths get reported, that will obviously change the mortality rate. So the previous virus that was similar to this is the SARS virus. And that ended up killing about 10% of people.
INSKEEP: Richard, is this one of these viruses where you are contagious before you are notably sick, you might not have any idea whether you're spreading it or not?
HARRIS: That is an open question. Obviously, it would be an important factor in the spread of the disease. That does happen, as you mentioned, like in the flu - measles that happens for. So it's not an unusual thing if it were to happen. But SARS, this previous coronavirus, seemed only to spread when it was symptomatic. Yesterday in a telephone news conference, CDC official Dr. Nancy Messonnier got a question on this point. And here's what she said.
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NANCY MESSONNIER: We at CDC don't have any clear evidence of patients being infectious before symptom onset. However, we are being - with our state and local health department partners - very aggressive and very cautious in tracking of close contacts to determine if we are able to identify any close contacts who indeed are ill. So far, we have not seen any human-to-human transmission in the United States.
HARRIS: And respiratory diseases, as I mentioned, are often spread through a cough. And that is, in fact, a symptom - right? - along with fever or shortness of breath for this one.
INSKEEP: How concerned are the experts here?
HARRIS: I spoke to an epidemiologist at the University of Toronto yesterday who said it will be hardest, by far, to get this epidemic under control in China because there are already so many cases. And each one has the potential to spread it further. Dr. David Fisman is trying to contain - says, trying to contain the epidemic in China is like being an outfielder and being told to catch, you know, 100 fly balls at once. He says the task is much easier here.
DAVID FISMAN: We're kind of getting knocked fly balls one at a time, and the job is not to drop them. But that's much easier than playing catch-up when you've allowed an epidemic to grow to a point where you have thousands of cases. And now you're trying to sort of track everyone down and prevent transmission.
HARRIS: So at this point, the CDC's message is that this is a serious condition, obviously, but we in the United States are currently at very low risk. It is always subject to change. But as long as there are just a handful of cases, as is the case right now, health officials can stay on top of it. The trick is to identify the sick people, to isolate them quickly, to keep an eye on their contacts and to make sure that the health care providers are also taking the precautions they need so they don't get sick themselves.
INSKEEP: Richard, thanks for the insights.
HARRIS: My pleasure.
INSKEEP: NPR science correspondent Richard Harris.
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