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Deadly Strain Of Bird Flu Is 'Most Lethal' Flu Virus Yet


At a briefing in Beijing today, World Health Organization officials describe the bird flu that's emerged over the past few weeks in China as one of the most lethal of its kind. The H7N9 strain is blamed for the deaths of more than 20 people, mostly in eastern China. But after a five-day investigation, officials say the source of the virus remains elusive. What have you heard about H7N9? What do you want to know? Give us a call: 800-989-8255. Email: You can also join the conversation on our website. That's at Click on TALK OF THE NATION. Joining us now from his office in Boston is NPR's science correspondent, Richard Knox. Always good to have you with us.

RICHARD KNOX, BYLINE: Good to be here. Thank you.

CONAN: And in previous cases of bird flu, generally, the villains are livestock - chickens.

KNOX: Yeah. One of the disturbing things about this to people who are, you know, follow the flu is that this virus doesn't makes or other birds sick - or at least not very often or not very noticeably. So it's been very hard to track in the environment, and it just kind of popped up when we first found these - when they first found these human cases about a month ago.

CONAN: And so we believe that the disease goes from birds, livestock, to people. But what was bout from person to person?

KNOX: Not so far. There are three clusters of cases in families where more than one family member has gotten sick. And so that might mean that in those cases, the virus from person to person, but not necessarily. It just might mean that the same person - I mean, you know, more than one person in the family got exposed to the infected chicken, or environmental contamination.

CONAN: Yet the fear, of cause, is these things evolve.

KNOX: Oh, yes. I think that's really the big fear on the part of the flu experts that I've been talking to. They, you know, this virus is clearly, genetically partially evolved to infect humans. That's why we're seeing these cases. So there has been genetic change so far - excuse me - that allows that, but not the genetic changes they would need in order to pass easily from human to human. And it could acquire that. But on the other hand, the H5N1 virus that flu experts have been following for 10 years has not yet learned how to do that, thankfully.

CONAN: And the scary part is if this new one does, it's particularly lethal.

KNOX: Yeah. And just to put it in a little bit context, as Keiji Fukuda - who's the WHO's top flu expert and who led this team to China that, over past five days, has tried to get a ground's eye view of what's going on there - he notes that this is one of the most lethal flu viruses known. So far, it has killed about 20 percent of the known cases. We might want to come back to that, because there may be others we don't know about. And comparably - compared to the H5N1 virus, that's deadlier. It's killed about 60 percent - triple that rate - over the last the last 10 years.

CONAN: But with such a small sample, do we really have a good idea of its nature?

KNOX: Yeah. That's one of the big unknowns. There's been at least one case in China involving a four-year-old boy in Beijing who seemed to have gotten the virus - or they're pretty sure he got the virus - without showing any symptoms. So that suggests that can happen. How often it happens is a total unknown, because there's no good quick antibody test yet to go around testing people who have been close to the known cases. So we don't know how big the iceberg is. We certainly know the tip of the iceberg are these 120 - excuse me - 108 cases who've gotten generally pretty sick so far. But that - you can't really calculate a death rate till you know the denominator, the whole iceberg.

CONAN: And in terms of response to this, yes, you start taking tests. Yes, you start to develop a genetic signature for it. But also, a lot of the time people start, well, killing the bird population.

KNOX: Yeah. Well, in fact that is a known proven way of limiting the spread of a disease that's spread by poultry and livestock, is to stamp it out or cull the infected herds. You can't really do too much of that in this case because, as I said, the chickens, the ducks, the poultry pigeons - you know, pigeons are a poultry item in China - don't get sick. So you can't really tell when a flock is infected.

One thing that seems to been effective, and they said that today in the conference in Beijing, is that closure of the live poultry markets in Shanghai, which is where this first appeared, seems to have slowed the number of cases emerging in that city.

CONAN: In Shanghai and - we're talking about Eastern China then.

KNOX: Yes. There are two municipalities and five provinces where this is - where the cases have come up so far, except for one in Taiwan today. We should come back to that. The - Shanghai seems to be the epicenter and the five provinces surrounding Shanghai. That's a really big area. That's like...

CONAN: And a lot of people.

KNOX: And a lot of people and, you know, hundreds of miles spread. So that's not a small area. There have been two reported cases in Beijing, one an eight-year-old girl who got sick and recovered, and the other her neighbor across the street, who is the case I mentioned who got the virus but didn't get sick.

CONAN: Yet you mentioned A) Beijing, a pretty fair distance from Shanghai, and Taiwan?

KNOX: Yes. Just today the Taiwanese reported an imported case. Not something that sprang up spontaneously there, but a man - 53-year-old businessman who traveled back and forth between Taiwan and a city called Suzhou - I'm not sure I pronounced it correctly. It's near Shanghai. And he got sick after he returned from Suzhou around April 12. So he clearly was infected there and brought it to Taiwan, which shows, not for the first time, that one of the issues with flu is that it can travel very easily in an age of air travel. He's in pretty rocky condition with respiratory failure in an intensive care unit in Taiwan.

CONAN: And that's one of the things that really does scare people, is getting on a plane with somebody else who's got it and then, well, the fear is everybody else on the plane gets it and they take off to all sorts of different points, and at that point it's hard to contain it. The important point to re-emphasize, though: so far no spread of this virus - this strain of the virus from one person to another person.

KNOX: That's right. They've been monitoring in China more than - well, more than 1,000 people, I think, by now who have been close contacts with the known cases. And they have not been finding spread from the cases to other people, except possibly in these, you know, like, three families and that's iffy. So I think right now we're not going to see an explosion. It would require something else, some unknown genetic factor that you can bet scientists are looking for, what that might be, in order to enable the virus to do that.

CONAN: Well, we'd like to hear what you've heard about this new strain of flu, what questions you have about it: 800-989-8255. Email us: And we'll start with Dave. And Dave is with us from Eagle in Idaho.

DAVE: Yes. I was wondering about the local population, if they're building up antibodies that would just maybe help protect them, whereas those of us who don't have chickens in the backyard aren't going to build that immunity.

KNOX: That's a very good question. Actually, it's a couple of points that are worth making there. One is that this - one of the things that's disturbing to flu experts about H7N9 is that never before have humans been known to get this virus, so there's presumably no pre-existing immunity out there in the population, unlike with H1N1 that caused a pandemic in 2009, as you remember. That's an H1 virus, and lots of, you know, practically the whole world has some level of protection against H1 viruses, which is why it didn't - wasn't as bad as people feared.

With this virus there is that danger. But the problem is we don't yet know how to test widely for antibodies against this virus. That's certainly something they're working on pretty frantically now so that we would get a sense of whether people out there who've been exposed developed antibodies and that might be protective. That's going to be a very important question regarding a vaccine if it's decided down the road that a vaccine is a good idea to make one, because we need to know what a vaccine would have to do in order to raise those protective antibodies.

CONAN: Thanks very much for the call.

DAVE: I have - can I follow up with...

CONAN: Sure.

DAVE: ...a question about - wasn't there like 1,000 or 1,500 dead pigs floating down a river? Where was that? Is there any connection?

KNOX: That was the river that goes through Shanghai. Yeah, there was a lot of worry about that. The best information I've seen is that there was no connection. They've discovered a pig virus in a lot of those dead pigs and they haven't - importantly, they have not discovered H7N9 flu virus in either those dead pigs or in livestock that are in slaughterhouses or farms.

DAVE: Thank you very much.

KNOX: Sure.

CONAN: Thanks very much for the call. We're talking with NPR's Richard Knox, and you're listening to TALK OF THE NATION from NPR News. And let's get Mary on the line, Mary calling us from St. Louis.

MARY: Hi. I have a question about this. I was wondering if a person or an animal that consumed poultry that was infected with the virus could get the virus.

CONAN: Yeah. Richard, if they don't know which animals have it and which don't, couldn't they end up in one of those slaughterhouses?

KNOX: Yes. (Technical difficulty) that's certainly a matter of concern. As I mentioned earlier, they've have been testing tens and tens of thousands of poultry around China and have found mysteriously few that are positive for this virus. So it's not at all clear how widespread it is in poultry or where.

The Chinese and the World Health Organization are saying that there's no evidence that people who eat poultry are at risk. You know, the usual precautions are certainly important, which is it needs to be cooked well. You don't want to eat chicken that's rare or pink.

And that, you know, people who prepare poultry should be, you know, wash their hands, wash the utensils that they use, wash the cutting boards and so on, because an uncooked infected chicken presumably could contaminate environmental services and get to humans.

CONAN: But again, no reason to believe this has left China or Taiwan?

KNOX: No. And also if, you know, if eating chicken were a big risk factor, we'd certainly have seen a lot more cases than we have.

CONAN: Mary, thanks very much. Let's go next to - this is Lisa. And Lisa is on line with us from Jonesboro in Arkansas.

LISA: Hi there.


LISA: It's delightful to hear that it's at this point not much of the concern that it's going to come stateside. But if it does, we do have backyard chickens and I have young boys. And I'm just wondering if there are things that can be done to make sure that we are able to protect ourselves and our family and our chickens.

KNOX: Well, first of all, I think you should stay tuned. We're trying to cover it and another media organizations are. And so I think you should watch what's happening in China to get some sense of whether it's becoming a bigger problem A) within China, or B) outside of China. I think there - certainly the surrounding countries such as Vietnam are extremely vigilant about exports of poultry from China right now. And I think that's going to be true here.

You know, I don't think there's much reason to worry right now about people bringing the H9 - excuse me - H7N9 virus from China to the United States and thereafter passing it to poultry. You know, that doesn't seem to be in the picture.

You know, downstream, you know, I think nobody really knows how this might evolve. I can bet that - pretty safely - that poultry experts in this, the Department of Agriculture and academic institutions, are watching carefully and probably starting to think about developing a poultry - a vaccine. But I don't know much more about that right now.


CONAN: Thanks very much.

LISA: Thank you so much. I will appreciate it.

CONAN: Thank you.

KNOX: Sure.

CONAN: And in the past, Chinese officials have either not been forthcoming in some cases, or in other cases may not have been aware of everything that's going on. Is there more confidence we're - this is under control in China?

KNOX: The World Health Organization has said today and frequently over the past month that they're very pleased with the way that Chinese have been conveying information to the World Health Organization and to the academic authorities who are following this. They have - they were very fast in sequencing the virus and publishing the sequence of several of the viruses that they recovered from patients in China, which really enables researchers everywhere to try to puzzle this thing out.

They invited this international team of flu experts - including Nancy Cox, who's the chief flu expert at the CDC in Atlanta - into China to look at the situation. I think the indications are that they're really doing everything they can, not to do - not to be charged of the same thing they were 10 years ago when SARS emerged and they really did try to cover it up for a critical period of time.

CONAN: And if the decision is made that a vaccine does need to be developed, we keep hearing about new technology that would make that faster. Is it here in time?

KNOX: Yes, it is, fortunately. There are ways of - so-called reverse engineering, where you start with the genes rather than with the virus and you make a synthetic virus that can be the basis for a vaccine. Basically what a vaccine is is a particular strain of virus that - then you can disable, make not infectious, inject into people safely and they will make antibodies to it.

The old way of making flu vaccines, which involves growing up the virus in millions and millions of eggs and then extracting the virus from the eggs and, you know, disabling it and then injecting it, is still around and that's the way we get most of our seasonal flu vaccine these days. They are pursuing vaccine on both fronts. You know, both the new kind of cell, so-called cell-cultured way, and the old-fangled egg way, because they want to be ready to make vaccine in a big hurry if they need to.

CONAN: And what is the next step?

KNOX: In vaccine production?

CONAN: No, no. What's the next step in monitoring the expansion or the spread of this particular strain, the H7N9?

KNOX: The next step is to - is for China to continue to test widely in animal populations, to try to figure out where this is coming from and whether it's regional and whether it's spreading. That's one of them. I think another next step, which has begun, is to study this virus really intensively. For instance, one of the things that scientists several labs around the country, around the world, are now doing, is to infect ferrets, these little weasel-like creatures which respond to flu the way humans do see if it spreads easily from ferret to ferret.

CONAN: Richard, thanks as always.

KNOX: Any time.

CONAN: Richard Knox, science correspondent for NPR News, joined us today from his office in Boston.

Tomorrow, states working to sign eligible Americans up for food stamps and what it's like to take SNAP for the first time. Join us for that. It's the TALK OF THE NATION from NPR News. I'm Neal Conan in Washington. Transcript provided by NPR, Copyright NPR.