Viral Superspreader? How One Man Triggered A Deadly MERS Outbreak : Goats and Soda In the past week, cases of the Middle East respiratory syndrome have more than tripled in South Korea. Researchers now have a clue to why the outbreak has grown so large, so quickly.
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Viral Superspreader? How One Man Triggered A Deadly MERS Outbreak

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Viral Superspreader? How One Man Triggered A Deadly MERS Outbreak

Viral Superspreader? How One Man Triggered A Deadly MERS Outbreak

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AUDIE CORNISH, HOST:

An outbreak of the deadly virus MERS in South Korea has set off alarms across the region. Here's the breakdown of the numbers right now. There are 36 confirmed cases and three deaths. About 1,600 people are quarantined. More than a thousand schools are closed. NPR's Michaeleen Doucleff reports on what we know about the virus and the chances that it could start the next big pandemic.

MICHAELEEN DOUCLEFF, BYLINE: For a virus to cause a pandemic, there's a top requirement. It needs to be able to spread easily from one person to the next, like the cold virus. And on the surface, MERS looks like a really scary version of the common cold. It starts off as a cough and a fever, and it's even in the same family of viruses as the cold. Vincent Munster is a virologist at the National Institute of Allergy and Infectious Diseases in Montana. He says there's a big difference between the two viruses - how they spread. The common cold infects the upper respiratory tract - your sinuses and your nose.

VINCENT MUNSTER: That's why you get those tell-tale signs of a common cold, so you got a runny nose.

DOUCLEFF: And stuffed-up sinuses, so when you sneeze, lots of virus comes flying out of your nose onto other people. And they can stick on things like doorknobs, your fingers. So the cold virus spreads very quickly. But Munster says the MERS virus couldn't care less about the nose.

MUNSTER: They really target directly the lower respiratory tract - the lungs.

DOUCLEFF: Deep, deep in the lungs, so when a person with MERS coughs or sneezes, not much of the MERS virus comes up. So the virus doesn't spread very easily. In fact, MERS is so lousy at spreading that people typically pass it on to just one person, if anyone. Outbreaks just peter out. So it looks like MERS cannot cause a pandemic. But then last month, something unusual happened. A man picked up MERS in the Middle East, brought it to South Korea, and then, it looks like he spread it to at least 20 people. That's right - two-zero.

MUNSTER: What we now see in South Korea is kind of interesting and kind of worrying, so we really have to figure out what's going on there.

DOUCLEFF: Has the virus changed or mutated in some way? Is it now more contagious and on its way to pandemic status? Well, Christian Drosten, a virologist at the University of Bonn in Germany, laughed at that idea.

CHRISTIAN DROSTEN: (Laughter). It's always possible that a virus can change. That's a general rule. But such a virus usually needs not just one but several of these changes, and the probability for these to happen together is really very low.

DOUCLEFF: Drosten has been tracking MERS in Saudi Arabia which has seen hundreds of cases. He thinks there's something else going on in Korea. He says sometimes people with MERS become super-spreaders.

DROSTEN: If we look at data that we have that are not published yet, what we can say is, there are some patients who have extraordinarily high viral loads.

DOUCLEFF: Their lungs just fill up with tons of MERS, so they're more likely to spread it.

DROSTEN: Some call them super-spreaders, right? And maybe the index patient in Korea was one of those people.

DOUCLEFF: And here's the key thing. Drosten says MERS super-spreaders are rare. So if his theory is right, people who caught MERS from the man who carried it to Korea won't pass the virus on to others, and the outbreak should be over in a week or so.

So you don't feel like this outbreak is something to be very alarmed about.

DROSTEN: No. I'm not alarmed. No, no. I think this is really within the normal range.

DOUCLEFF: And even if his theory is wrong, Drosten says South Korean health officials are doing everything they can to stop the outbreak. Michaeleen Doucleff, NPR News.

CORNISH: OK. NPR's Brian Naylor. Thanks so much.

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