美国国家公共电台 NPR Why Chinese Scientists Are More Worried Than Ever About Bird Flu（在线收听）

RACHEL MARTIN, HOST:

Now to China, where a strain of bird flu has killed a record number of people this year. Scientists on the frontlines of this deadly strain are more worried than ever about its potential to spur a global pandemic. NPR's Rob Schmitz has this story.

ROB SCHMITZ, BYLINE: At a research lab on top of a forested hill overlooking Hong Kong, scientists are growing viruses.

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SCHMITZ: They drill tiny holes into an egg. Next, they'll inoculate it with avian influenza to observe how the virus behaves. This lab at Hong Kong University is at the world's forefront of our understanding of H7N9. It's a deadly strain of the bird flu that's killed more people this season - 162 - than when it was first discovered in humans four years ago. That worries lab director Guan Yi. But what disturbs him more is how fast this strain is evolving.

GUAN YI: (Through interpreter) We're trying our best, but we still can't control this virus. It's too late.

SCHMITZ: Guan is one of the world's leading virologists. His work on Severe Acute Respiratory Syndrome, or SARS, in 2003 helped China's government control the virus that had killed hundreds, avoiding a second outbreak. He's now moved on to avian influenza.

His lab is full of tissue samples from chickens, ducks and humans, all who have died from H7N9. The samples arrived from a network of scientists who purchase birds at live poultry markets throughout southern China. Back in December, Guan and his colleague Zhu Huachen began noticing something strange.

ZHU HUACHEN: Some of the birds, if they look severely sick, then we purchase the birds. And then they would die within a day.

SCHMITZ: They were chickens infected with H7N9. That was strange because chickens normally could live with the virus in what's known as a low pathogenic state. Guan and his team discovered the H7N9 strain had now mutated into a new lethal form inside of chickens.

GUAN: (Through interpreter) Ten years ago, H7N9 was less lethal. Now it's become deadlier. Before, it barely affected chickens. Now many are dying. Our research shows it can kill all the chickens in our lab within 24 hours. If this latest mutation isn't stopped, more will die.

SCHMITZ: Which could be very bad news for the global poultry industry. What worries Guan more is H7N9 has proven an ability to mutate quickly. And in the rare cases when humans catch it, more than a third of them die. He fears a future mutation might make the virus more transmissible between humans.

GUAN: (Through interpreter) Based on my 20 years of studying H7N9, the virus itself as well as how the government handles it, I'm pessimistic. I think this virus poses the greatest threat to humanity than any other in the past 100 years.

SCHMITZ: Guan's choice of 100 years is deliberate.

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UNIDENTIFIED JOURNALIST: For this day, November 11, 1918, marks the end of an era of hate and bloodshed and violence.

SCHMITZ: A newsreel from a Victory Day parade after World War I allows only a brief passing reference to what was called the Spanish flu.

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UNIDENTIFIED JOURNALIST: Grotesque and ugly in their influenza masks, the people of San Francisco celebrate.

SCHMITZ: As the war drew to a close, the global pandemic killed between 20 and 50 million people, all dead from a flu that originated in birds.

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UNIDENTIFIED JOURNALIST: And so San Francisco celebrates in 1918 because the war is over, and there will never be another.

SCHMITZ: In the century since, there have been more wars. And Dr. Guan Yi says it's not a stretch to envision another global pandemic.

GUAN: (Through interpreter) Today, science is more advanced. We have vaccines. And it's easy to diagnose. On the other hand, it now takes hours to spread new viruses all over the world.

SCHMITZ: Many of these viruses are first discovered in China, a country with scores of small poultry farms run by farmers who aren't well educated about the threat of bird flu and who often hide evidence of infected birds to protect their bottom line.

GUAN: (Through interpreter) Farmers are scared of losing money. I know how they think. I'm from a rural part of China, and that's why I'm not optimistic about this.

SCHMITZ: The real test, of course, is how transmissible a future mutation of the flu is between humans. But when it comes to poultry, Guan says there are some encouraging signs. Big cities like Shanghai have quickly shut down their live poultry markets when human cases are on the rise.

But that's just China. Guan says preventing the next global pandemic will depend on how well the governments of individual countries collaborate with each other. That, he says, is a different challenge altogether. Rob Schmitz, NPR News, Hong Kong.