AVIAN FLU: Q&A / WENDY ORENT
Author And Anthropologist: Bird Bug Has Flown The Coop
Richard Halicks – Atlanta Journal Constitution
Sunday, October 23, 2005 - To become a global killer, avian flu must do two things: develop a reliable way to move from one human to another while maintaining its demonstrated ability to kill. An Atlanta science journalist and author believes bird flu can do one or the other of those things, but not both. Wendy Orent, author of "Plague: The Mysterious Past and Terrifying Future of the World's Most Dangerous Disease," dismisses what she calls the "flu chorus" -- a group of scientists and public policy experts who warn that bird flu has put the world on the cusp of calamity.
They point to the devastating Spanish flu outbreak in 1918 and worry that avian flu has much in common with that 1918 virus. Orent, too, looks at the 1918 pandemic but sees the opposite: the reason that this current strain of flu won't become a pandemic. Orent holds a doctorate in anthropology from the University of Michigan. But her interest lies in the field of evolutionary epidemiology -- how and why bugs evolve into killers, or don't. She says that the peculiar conditions of the world in 1918, particularly World War I in Europe, led to the Spanish flu pandemic, and that such conditions don't exist today. "You had a huge number of people in the trenches, in hospitals, in trucks being shuttled all over the western front, in trains, in ships -- these ships were just breeding grounds for disease," Orent said. Those conditions constituted what she and others call a "disease factory," an unusual set of circumstances in which a very deadly bug learns how to move among people. Orent spoke on the phone last week with The Atlanta Journal-Constitution's Richard Halicks. Here is an edited transcript of that interview. She begins, referring to World War I: When you have people who are immobilized by illness, so ill that they can't move, and they are very, very close to healthy people who might have a broken leg, or have been wounded in some way -- but who don't have the flu -- you can infect them very easily. And there's no cost to the virus in being very, very virulent. Now what is virulence? Virulence is the ability to exploit a lot of the host's tissues, and to make the host very sick, and to be lethal. Q. When you say there's no cost to the virus, what do you mean by that? A. Transmissibility is the ability of the virus to get out of one host and into another. In order to do so, the virus has to do something to the host to get itself shed. People act like transmissibility is just some little quirk of the genome, but what it really is, is the ability of the virus to colonize tissues, say, in the upper airways so that you sneeze or cough, and the virus is shed in large quantities. … You might go to work one day not feeling terribly well. You try not to sneeze all over everywhere. But flu is extraordinarily transmissible. It's these tiny, tiny particles that just fly off in a big cloud [when an infected person sneezes] and spread very easily…so flu depends on keeping you out there -- going to work, you know, going to school, sitting on a bus -- if it's going to spread. It has to keep the host relatively healthy. A host can't keel over and die. Think about how ebola doesn't spread because it's so lethal that it just kills you right off. And certain forms of plague can do that, too. They kill you very quickly so there's no chance for the bug to spread…so if transmissibility increases, the virulence should decrease, because the virus needs to keep you mobile to get you to transmit it. If you think about it, it's just Darwinian logic. If you're too sick to transmit the disease, it dies with you. Q. In effect, it kills itself by killing you? A. Yes…H5N1 is a wonderfully deadly disease -- if you're a chicken. It's very well-attuned to exploiting chicken tissues. It actually becomes a systemic disease in chickens, which even the World War I flu didn't do in humans. It remained a respiratory infection. H5 can affect a chicken's entire body, and it keels over and dies.
The thing is, bird flu is bird flu. And human flu is human flu. When you hear people talk about avian flu, and they say, "Well, all it has to do is mutate to transmissibility," I just tear [out] my hair. What does that mean? It means it has to start infecting people in the upper airways. It has to make them sneeze and it has to make them cough. It has to do all the things it's not doing now. The autopsy reports [on those killed by avian flu] show virus-infected tissues only deep in the recesses of the lungs, in the alveoli. You don't find any of them in major airways. This is really significant: The people taking care of these patients do not get sick.
So people are not thinking when they say, "It's going to mutate to transmissibility." They don't realize how big a step that really is. Since we don't have World War I, and we don't have trenches and hospitals of that sort, and, you know, death ships, we don't have disease factory conditions that would allow the maintenance of virulence in human flu. When it starts transmitting person to person, the virulence will go down, and it should go down to the level of an ordinary pandemic flu; i.e., 1957 or 1968, because the conditions to support extreme virulence do not exist. Q. You assert that we don't know H5N1's mortality rate. A. We have no clue. Q. How come? A. They haven't done the necessary testing. You have to do blood sampling of all these chicken farmers to find out whether there is evidence of H5 antibodies in their blood. Take Thailand. I've got a correspondent in Thailand who's been watching this very closely. And he writes to me that there has not been a single case among chicken farmers or [slaughterhouse] workers in Thailand of death from H5N1. How can that be? If this is such a deadly virus, here you have people living with the virus, selling the chickens, killing the chickens, being exposed to who knows how much -- and they're not getting sick. Why not? Chances are they're already immunized. They didn't get sick, or they had a mild infection, and they're all immune. So we could be talking about a giant population of immune people in southeast Asia. If, say, a million people were infected and 60 died, this is not a very impressive death rate. Q. The CDC says it is now getting upward of a half-million visits to its avian flu site daily. People seem genuinely worried about this. A. Dead ducks don't fly. Or at least they don't fly far…we've got to be a little bit more cautious and thoughtful. I don't think it's necessary to jump on every disease bandwagon and say, "This is the big one! This is the big one!" Well, bio-terrorism didn't prove to be the big one. And mosquito-borne diseases didn't prove to be the big one. And now this is not going to prove to be the big one. At some point, the public is going to get angry and say, "Hang on a minute. Why should we believe anything you say?" The thing is, there are risks out there, but you have to take a thoughtful look at the ability of each disease to constitute a genuine risk.
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