“Extreme remedies are most appropriate for extreme diseases.”
-Hippocrates3039
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The chief of virology at Hong Kong’s Queen Mary Hospital believes that “the cause and solution [of H5N1] lies within the poultry industry.”3040 The diagram to the right, from the U.S. Department of the Interior’s August 2005 report on the bird flu threat,3041 illustrates the key role domestic poultry play in the development of pandemic influenza.3042 All influenza viruses start in waterfowl, but there does not seem to be direct spread from the natural duck reservoir directly to mammals or humans; domesticated fowl are required as the stepping stone. The most a wild duck virus seems to be able to do to a person is cause a mild case of pinkeye.3043
The scientists who unsuccessfully tried to infect human volunteers with wild duck viruses in the lab even tried passing the virus from one person to the next to enhance human infectivity. They squirted a million infectious doses up the first person’s nose, then inoculated a second person with the first person’s mucus, and continued down the line. Despite the high doses used and five person-to-person passages, the virus still could not grab hold. A study published in 2006 in Clinical Infectious Diseases found that pig farmers are up to 35 times more likely to show evidence of swine flu exposure than those with no occupational contact with pigs,3044 but studies of Canadian wildlife personnel have consistently found them negative for waterfowl virus infection.3045 Although one duck hunter and a few wildlife professionals tested in Iowa showed evidence of exposure to wild bird viruses,3169 influenza viruses found in their natural undisturbed state do not seem to pose a human threat.
Maybe if duck viruses could squeeze 20,000 humans into one big elevator they might be able to get somewhere. Getting 20,000 chickens together in an enclosed space is not only easy, it happens all the time, allowing for millions of passages of viruses through cells and susceptible hosts who have nowhere to run. In this way, the virus can be amplified3046 and perhaps adapt to humans by proxy. Thanks to that evolutionary quirk of nature—the certain molecular resemblance of the respiratory tract of a chicken to our own—as the virus gets better and better at infecting and killing chickens, it may be getting better and better at infecting and killing us.
According to a senior molecular virologist at the University of Cambridge, “Chickens provide a bridge between the wild bird population where avian influenza thrives and humans where new pandemic strains can emerge. Removing that bridge will dramatically reduce the risk posed by avian viruses to humans.”3047 If domestication of poultry is the bridge,3048 it’s a bridge that can be burned.
The domestication and captivity of birds have created biohazards like Salmonella, Campylobacter, Psitticosis (parrot fever), and avian tuberculosis. Most seriously, it brought us influenza. “Like most aspects of what is normally celebrated as progress, the domestication of animals had a downside,” wrote one Massachusetts Institute of Technology professor of history.3049 Pandemics of influenza may be one such downside.
If the development of animal agriculture marked the “start of the era of zoonosis,” as the dean of Michigan State’s veterinary school asserts, then the scaling back of animal agricultural production may hasten its end.3050 In hopes of severing the link from the viral reservoir, there are those at the FAO who have suggested that domestic duck farming be abolished.3051 Ducks were domesticated 150 generations ago,3052 3053 a blink in human evolution.3054 While ending the domestication of ducks would not alleviate the current crisis, since H5N1 has already flown the coop, it may help prevent future pandemics.3055
“Prevention of H5N1 avian influenza in humans is best achieved by controlling infection in poultry,” advises the WHO.3056As noted by the dashed lines in the Department of the Interior’s diagram, though, not only has H5N1 jumped directly from chickens to humans, it has pulled off one of its greatest tricks yet—a homecoming of sorts—reinfecting waterfowl. By retaining its lethality for chickens and humans while remaining relatively harmless for migratory birds, the Z mutant of H5N1 has created a monster, enabling the presumably factory-farmed virus to wing itself around the world. At this stage, the prospect of eradication seems remote.3057
A leading flu authority at Mount Sinai School of Medicine once remarked that if you eliminated the ducks in the world, you’d essentially eliminate pandemic influenza.3058 “But you can’t kill all the ducks and aquatic birds of the world—that would be absurd,” says Webster. “It makes you realize that influenza is a noneradicable disease.”3059 The influenza virus itself, as it exists in nature, may be “noneradicable,” but we don’t care what happens naturally inside the guts of wild ducks—and the ducks don’t seem to either. It’s the human pandemic variety we want to get rid of, which may be possible if we remove the stepping stones by which the virus hops from the rice paddies of Asia to children hop-scotching in Europe.
According to the U.S. Geological Survey, “Currently there is no evidence that humans have been affected with H5N1 influenza virus through contact with wild birds. All reported human infections have been associated with contact with domestic poultry.”3060 In theory, then, the solution to preventing future pandemics, and maybe even stopping the potentially impending pandemic in mid-flight, is to kill all the chickens.
H5N1 has been stopped before. “It was fairly obvious,” Shortridge said, recounting Hong Kong in 1997, “the chickens had to go.”3061 And it worked—killing all the chickens in the territory eliminated the virus. Genetic analyses of the H5N1 strain that arose four years later show that it emerged independently, jumping again from the natural duck reservoir to chickens. Hong Kong tried killing all the chickens once again, but it was too late. Leading scientists advocated ridding the entire territory of chicken farms, banning imports, and closing down poultry markets, but H5N1 had already escaped.3062
Dutch virologist Jan de Jong, to whose lab the defining human Hong Kong virus was originally sent, scoffs at the limited culling of hundreds of millions of chickens as too little too late. “These measures are really nonsense,” he said in a telephone interview. de Jong suggested that a near-total culling of Asia’s poultry and the curtailment of poultry farming for several years would be the only way to stop the H5N1 outbreaks.3063 Osterholm seems to agree. “So even though we talk about having killed off 300 million chickens in trying to reduce it,” he said, “we turn over billions of chickens a year in China just for food supply. Each one of those that are born and hatched are brand new incubators for the virus, too, so we keep resupplying this susceptible population, we keep allowing this.”3064 H5N1 keeps taking shots at sustained human-to-human transmission; by repopulating the global poultry flock we keep reloading the gun. Both scientists realize, presumably, the economic implications that make such a solution a political impossibility.
Given H5N1’s spread to Europe, the mammoth slaughter would have to extend far beyond Asia, and because the same underlying conditions of emergence would remain, the cessation of poultry production would have to remain indefinitely. “As long as the kettle is on the fire, the water temperature will continue to rise until it reaches the boiling point,” the World Health Organization’s representative in Thailand explained. “The pandemic threat will not go away because we don’t have a way to put out the fire yet.”3065 Yes, but we could remove the kettle. Let the flame of influenza continue to flicker in wild waterfowl, but we could, in theory, remove the middleman kettle of poultry production in hopes of preventing influenza from boiling over into the human population.
The logical extension of the effective 1997 Hong Kong strategy is to kill off the entire world’s chicken flock. Lest this sound too extreme, that’s already what happens to most of the world’s broiler chickens every six weeks or so. Meat-type chickens have been bred to grow at such accelerated speed that the global broiler flock is essentially slaughtered every handful of weeks and replaced with hatchling chicks. Logistically, killing off all commercial chickens in the world is easy—we have them all locked up. The slaughtering apparatus is in place and already undergoes trial runs about every month or two. If, instead of restocking, humanity raised and ate one last global batch of chickens, the viral link between ducks and humans might be severed, and the pandemic cycle could theoretically be broken for good. Maybe bird flu could be grounded.
The Centers for Disease Control and Prevention understands the human health risks of the “ongoing intensification and consolidation of the food-animal industry,” but acknowledges the protein demands of a growing global population. The deputy director of the CDC’s Office of Global Health described the dilemma simply as “we want more protein while not jeopardizing human health.” However, only a trivial percentage of the world’s calories (1%) and protein (3%) come from poultry.3066 3077 Technically, there is no human nutritional need for any animal protein. In fact, according to the Harvard University School of Medicine, the healthiest sources of protein are “beans, nuts, grains and other vegetable sources of protein.”3068 One reason India is not considered a high-risk area for novel influenza strains is reportedly that a large portion of the population is vegetarian.3069 Regardless, from a pandemic standpoint, it doesn’t matter whether one switches to beans or to beef; what matters is breaking the feathered link in the chain.
Smallpox could be eradicated because there is no contemporary nonhuman animal reservoir. Unlike influenza, in which human beings are considered “irrelevant for the viruses’ survival,”3070 the smallpox virus only existed in humans and so could be vaccinated out of existence since there was no source of new genetic material.3071 It is no coincidence that 11 out of the top 12 most dangerous bioterrorism agents are zoonotic pathogens.3072 How else can you infect millions unless you pull something out of the animal world—a rabbit out of the hat, but in reverse? The human immune system would therefore have no prior exposure, and the infection could slip beneath the body’s radar. By cutting influenza’s genetic supply lines to the animal world, no more pandemics would presumably be possible.
What would happen to human influenza if its relationship to the avian reservoir were severed? People would still get the flu, but our bodies would be hip to it. The virus would continue its genetic drift, accumulating mutations in its outer coat so as not to be utterly routed, but no longer would there be fresh virus to swap genes with. In other words, no more viral sex. Eventually, without continued intrusions of restless alien viruses backed into new evolutionary corners, along with the presumed extinction of pandemics, we might even expect seasonal influenza to lose virulence gradually with time as it achieved more of a balance. According to Webster, it’s been this “irregular infusion of avian virus genes into the human virus gene pool” that has prevented human influenza viruses from “reaching an evolutionary equilibrium with their hosts.”3073 The evidence is as easy as learning influenza’s ABCs.
There are three types of human influenza viruses: A, B and C. Influenza A is considered the only type of influenza that can cause pandemics, because influenza A is the only type of influenza with an active link to the animal world. The influenza viruses ever bubbling forth from waterfowl are influenza A viruses that may cross over and establish themselves within poultry and pigs and people. Influenza B and C viruses are thought to have originally arisen the same way as influenza A viruses (from waterfowl, centuries ago), but they’ve circulated and adapted to the human race for so long—hundreds or even thousands of years—that they can no longer reassort with avian viruses.3074 They’ve evolved into new species in the biological sense that they can no longer reproduce with their ancestral progenitors to create viable offspring. They are now strictly human viruses; the avian umbilical cord has been cut.3075
As such, influenza B and C viruses are old hat to humanity’s collective immunity. They never cause pandemics and, in general, result in milder disease. Influenza C has presumably parted ways with its avian ancestors to such an extent that it rarely causes clinical disease at all.3076 If influenza C viruses manage to cause any symptoms, the infection more closely resembles the common cold than the flu.3077 And that is what we might expect all human influenza viruses to evolve toward in a pandemic-free world cut off from the avian reservoir.3078 Without chickens, the worst that may bubble up from that viral volcano is a rare case of pinkeye resulting from sweeping duck manure or forgetting to turn our heads should sneezing seals not properly cover their mouths.
Instead of letting the world’s chicken flock vanish, can’t they all be vaccinated? As we know from our own flu shots, which have to be reformulated every year, the influenza virus may be too slippery to be stopped by vaccination because of its high rate of mutation. Vaccination can keep birds superficially healthy, but may not stop the replication and excretion of the virus.3079 While vaccinated birds may not get sick (so profitability is not diminished), chicken sheds may remain breeding grounds for superflu viruses.3080 In fact, vaccination may even select for more virulent mutants. Webster is particularly concerned about China’s plan to vaccinate its 14 billion-strong poultry flock.3081 “[P]athogens can evolve to more virulent pathotypes in vaccinated herds or flocks,” reads one virology textbook, “especially when animals are held under intensive production systems.”3082
As long as there is poultry, there will be pandemics. It may be us or them. One consequence of the evolutionary stability of the waterfowl reservoir is that the pandemic precursors will always be waiting in the wings.3083 Influenza viruses mutate at the same rate in wild ducks as in any other species. These duck viruses have over millions of years reached peak fitness such that any net change in any direction makes new mutants a little less perfect and they are selected against and nudged out of the applicant pool. The mutant swarm in aquatic birds is always correcting itself. Viral mutants continue to arise that may be just a little better at infecting chickens and humans, but are quickly outmaneuvered by the duck optimal variant. As soon as that swarm of viruses is forced into a new environment, though, any mutants for which a growth advantage exists may be quickly selected. The pandemic potential of the virus has existed, and continues to exist, ready to blast off if given the opportunity. Our role is to try to keep it in the ducks and not provide the virus an enormous lab of feathered subjects to tinker in. Noting the emergence of zoonotic diseases in general is largely a product of human activity, FAO researchers conclude that “the solution to these problems is also a matter of human choice.”3084