Bird Flu: A Virus of Our Own Hatching

Bird flu is caused by a common — and usually harmless — virus found in ducks, but in recent years highly virulent strains have emerged that have caused massive losses of chickens and other domestic birds raised for food.

When an outbreak has occurred, traditionally the virus has been stamped out by quickly destroying all infected and exposed birds. In the United States, 17 million birds were killed in Pennsylvania due to the H5N2 strain of the bird flu virus in 1983 to 1984, and 200 million birds in Eurasia and Africa have been killed due to the H5N1 strain since 2004.

Needless to say, the poultry industry is terrified of bird flu, but not just because of its avian victims: The H5N1 flu strain arising out of Asia also has killed about 200 people. The last time a bird flu virus adapted to humans, it triggered the flu pandemic of 1918, which killed an estimated 50 to 100 million people around the globe.

Experts believe that as long as poultry is being raised in stressful, filthy, overcrowded conditions, virulent strains of this virus will continue to arise. The poultry industry is eager both to protect their huge flocks from bird flu outbreaks, and to downplay the connection between the high-risk conditions in their poultry sheds and the propensity these conditions have to facilitate the emergence of deadly strains of the virus.

Laying Blame

Migrating birds have been easy scapegoats. Unfounded claims that wild birds were to blame for the spread of dangerous strains of bird flu were used as a smokescreen to take the focus off industry practices and government policies. But the blanket of protection is being pulled away. A 2006 international science conference, sponsored by the world’s leading veterinary and agricultural authorities, came to the consensus that the main means by which this virus is spreading globally is not via migrating birds, but rather the multibillion dollar commercial trade in poultry products.

For example, Britain has more than 10 million free-ranging chickens, but when the deadly Asian strain of bird flu H5N1 first struck the poultry industry earlier this year, it didn’t hit an outdoor flock — it hit an industrial facility owned by the largest turkey producer in Europe, leaving 160,000 turkeys dead. Likewise, the first outbreaks in Africa and continental Europe occurred in factory farms.

Bird flu is traveling more along the railways and highways than the flyways. Not surprisingly then, when this disease lands, it’s more likely to affect those vertically integrated, globalized and industrialized conglomerate poultry empires rather than small, independent producers serving local markets. During the British outbreak in January 2007, leaked memos showed that the government initially colluded with the industry to cover up that a corporation, Bernard Matthews, was trucking in more than 40 tons of meat from H5N1-stricken Hungary every week. As one biologist remarked, one reason fingers continue to point to wild birds is that “corporations pay more taxes than migratory birds do.”

The spread throughout Asia seems to have followed the same pattern. Some officials alleged that backyard flocks were at higher risk than those housed in enclosed industrial facilities. But when public health researchers from Johns Hopkins University looked into the matter, they found just the opposite. Publishing their findings in a December 2006 Food and Agriculture Organization of the United Nations report, they found that industrial-scale chicken and egg operations in Thailand were proportionally four times more likely to suffer H5N1 outbreaks than small flocks kept outdoors. Never once has such a virus been known to emerge in a pasture-raised chicken flock — the only scientific study to date on the subject has revealed that industrial facilities are at the highest risk for spreading this virus as well.

The Culprit: Industrial Ag

The globalization of this Westernized industrial model of poultry production has not only facilitated the spread of deadly viruses like H5N1, but also plays a role in their emergence in the first place. After all, people have been raising birds in their back yards for thousands of years and birds have been migrating for millions. Only in recent years have we seen an exponential increase in the number of outbreaks of highly pathogenic (disease-causing) strains of bird flu. As leading flu scientist Ilaria Capua remarked, “We’ve gone from a few snowflakes to an avalanche.”

The world’s foremost expert on bird flu, Robert Webster, director of the U.S. Collaborating Center of the World Health Organization, was asked by the senior correspondent of the TV show “NewsHour with Jim Lehrer” to identify the “change in conditions that suddenly lit a match to the tinder” — in other words, what started the avalanche. Dr. Webster replied:

“Farming practices have changed. Previously, we had backyard poultry. I grew up on a farm in New Zealand. We had a few backyard chickens and ducks. The next door neighbor was so far away it didn’t matter. Now we put millions of chickens into a chicken factory next door to a pig factory, and this virus has the opportunity to get into one of these chicken factories and make billions and billions of these mutations continuously. And so what we’ve changed is the way we raise animals.”

Dozens of heritage poultry breeds used to peck around America’s barnyards. Now chickens raised for meat have been bred to be nearly genetically identical, and are typically warehoused in massive sheds containing tens of thousands of birds standing in their own waste. This global monoculture of tens of billions of birds bred for rapid weight gain creates conditions ripe for viral survival, mutation and dispersal. U. S. Department of Agriculture researchers conclude: “Selection of poultry for fast growth rate is often accompanied by a reduction in specific immune responses or increased disease susceptibility.”

In contrast, outside in the open air, influenza viruses quickly dehydrate and die, or are rapidly killed by the UV rays in sunlight. Just as this industrial model has been linked to mad cow disease, deadly strains of E. coli in cattle and multi-drug resistant Salmonella in eggs, the big recent shift in the ecology of avian influenza has been the intensification of the global poultry sector.

Preemptive Strikes

In October 2005, the United Nations specifically called on governments around the world to address factory farming’s involvement in the spread of avian flu: “Governments, local authorities and international agencies need to take a greatly increased role in combating the role of factory farming, commerce in live poultry and wildlife markets which provide ideal conditions for the virus to spread and mutate into a more dangerous form.”

Some governments are heeding that call. The 27 countries of the European Union, for example, are phasing out the small, wire “battery” cages for egg-laying hens that still are used in about 95 percent of egg production in the United States. Europeans also are working toward decreasing the stocking density of broiler chickens. “In the agricultural sector, greater account needs to be taken of the implications of intensive animal husbandry practices,” said Markos Kyprianou, the European Commissioner for Health and Consumer Protection. “Public health policy needs to have a much greater role to ensure human health protection. Policies need to encourage a shift away from intensive rearing … at an international level.”

In the United States, consumer pressure has moved corporations to preempt government action. Recently, such major buyers of animal products as Burger King, Hardee’s, Carl’s Jr. and Wolfgang Puck have announced policies with improved animal welfare standards. This year the largest pork producer in the world, Smithfield Foods, announced a phase-out of the use of gestation crates — small stalls for pregnant pigs — and the leading U.S. veal producer pledged to eliminate veal crates, calling them “inhumane and archaic.” These steps reflect what could become a sea change in public opinion on industrial animal agriculture in the United States, and these improvements can have positive consequences for human health.

Viral Mutability

The way we treat animals has global public health implications. Most new infectious diseases in recent decades have emerged from animals, and not without human intervention. Whether it’s the African bushmeat trade implicated in the AIDS epidemic, tropical deforestation linked to Ebola, live animal markets and SARS (Severe Acute Respiratory Syndrome), or cannibalistic feeding practices and mad cow disease, our exploitation of the natural world is coming home to roost.

The highly infectious avian flu strain H5N1 is currently almost exclusively a bird virus. Hundreds of millions of birds have died, but only a few hundred people have become infected. Of those infected though, more than half have died. What keeps the world’s public health authorities awake at night is the possibility that this virus might mutate into a human form, easily transmissible from one person to the next, and thereby trigger the next influenza pandemic. It’s happened before.

In 1918, a bird flu virus spawned one of the worst plagues in human history, a flu pandemic killing millions and infecting half the world’s population. The virus is thought to have gained its virulence in soldiers trapped by the millions in the crowded, stressful, unhygienic conditions of World War I. From the point of view of this virus, these same trench warfare conditions exist today in industrial chicken and egg operations around the world, offering billions of feathered “test tubes” for viruses to incubate and mutate within — billions more spins at pandemic roulette.

Most experts believe that another flu pandemic is inevitable, but we don’t know when it will strike or how bad it will be. Given the unprecedented spread of the H5N1 virus, there is worldwide apprehension in the scientific community that another pandemic is imminent. Hopefully this current level of concern will spur us to action, to better prepare our communities and, perhaps, to recognize the many hidden costs of cheap food.

Reversing course away from raising birds by the billions under intensive confinement, and towards more sustainable, organic methods of production can decrease the risk of the emergence of future highly pathogenic flu viruses, but H5N1 has already hatched. There seems little hope in eradicating this virus now that it has become endemic in the ecosystems across two continents. This means that we should all be prepared to take practical, concrete steps to mediate the impact if a pandemic threatens our families and communities. See "Surviving the Next Pandemic" below to learn more about how to protect yourself.

Influenza Evolution: From Ponds to People

The avian influenza virus has existed for millions of years as an innocuous, intestinal, waterborne infection of aquatic birds, harmless to both birds and people. So what has caused a duck’s harmless intestinal bug to become a threat to humans?

In people, a virus must make us sick in order to spread; it has evolved to make us cough to shoot the virus from one person to the next. In the avian influenza virus’ natural reservoir though, the duck doesn’t get sick, because the virus doesn’t need to make the duck sick to spread. In fact, it’s in the virus’ best interest for the bird not to get sick, so it can spread even further. After all, dead ducks don’t fly. Instead, the virus silently multiplies in the duck’s intestinal lining, is excreted into the pond water, and then is swallowed up by another duck — so the cycle continues as it has for millions of years and no one gets hurt.

But when ducks are raised in crowded indoor conditions, or are crammed into cages stacked high enough to splatter virus-laden droppings over land-based birds like chickens (a problem at live bird markets common in Asia and some American cities), then the virus has a problem. Like a fish out of water, when the virus finds itself in the gut of a chicken, it no longer has the luxury of being spread easily — chickens aren’t paddling around in the pond. The virus must mutate or die. Unfortunately for us, mutating is what influenza viruses do best.

In aquatic birds, the virus is perfectly adapted in totally harmless evolutionary stasis. But, when thrown into a new environment — such as that of terrestrial birds in crowded conditions — it quickly starts mutating to adapt to the new host. In the open air, the virus must resist dehydration, for example, and may have to spread to other organs to find a new way to travel. In this case, new flu virus strains have found the lungs and become an airborne pathogen, which is bad news for humans.

World Health Organization Links Flu to Poultry Industry

In the introduction of “The World Health Report 2007,” recently released by the World Health Organization (WHO), Director-general Margaret Chan noted that when the organization was founded around 60 years ago, the infectious disease situation was relatively stable and new diseases were considered rare. “Since then, profound changes have occurred in the way humanity inhabits the planet,” she writes. Now, the disease situation is “anything but stable.” In part because of “intensive farming practices, environmental degradation, and the misuse of antimicrobials,” she notes that new infectious diseases are now emerging at a rate unprecedented in the history of medicine — nearly 40 new diseases since the 1970s, approximately one new disease every year. During the last five years, the WHO has verified more than 1,100 epidemic events worldwide.

Speaking at the launch of the report, she specifically singled out poultry production. “The intensity of poultry farming is such that we really need to look at how the human-animal interface is managed. It should not come as a surprise that we are seeing more and more disease outbreaks coming from the animal sector.” Similarly, a research report released this summer by the Food and Agriculture Organization (FAO) of the United Nations suggests that the industrialization of animal agriculture in recent decades is increasing public health risks on a global scale.

In 1980, nearly all chickens in China were raised outdoors in small, traditional backyard flocks. By 1997, though — the year H5N1 arose in Hong Kong — approximately half of the 10 billion chickens in China were intensively confined in more than 60,000 industrial facilities, a few of which raised more than 10 million chickens at a time. An article published by scientists in Vietnam and Thailand in the Annals of the New York Academy of Sciences explains why such facilities may be particularly risky:

“The large concentration of animals farmed in overcrowded conditions in industrial batteries (several hundreds or even several thousands of individuals in a confined space), provides an extremely infectious context through contact with numerous pathogens, as opposed to natural extensive or semi-extensive breeding conditions ... The numbers and density in which animals are bred result in overcrowded conditions, which, among other things, stress the animals, modify their metabolic performances, weaken their immune system, and above all maintain a high risk of hyperinfection by massive infectious loads ... Where a small infectious dose would naturally be controlled by a normal immune system, there is no chance, even for an efficient immune system, of controlling huge infectious doses which ‘saturate’ defense effector mechanisms and ‘overflow’ the animals’ immune mechanisms ... ”

In “The World Health Report 2007,” the WHO reiterated that an influenza pandemic currently poses the greatest threat to international public health and that the “question of a pandemic of influenza from this virus [H5N1] or another avian influenza virus is still a matter of when, not if.”

The Asian scientists offer a potential solution: “Possible alternatives that would reduce the risks of contact could, for instance, include replacing large industrial units with several smaller-scale production units containing lower densities of animals. In other words, this means favoring humane treatment and product quality over industrial yield. There are many advantages to this: animals would be less stressed and thus more resistant to infectious aggressions; contact between individuals would be less intense, which would reduce infection rates since infectious doses would be lower.”

The FAO report “Industrial Livestock Production and Global Health Risks” is available here. Also see The Potential Role of Concentrated Animal Feeding Operations in Infectious Disease Epidemics and Antibiotic Resistance.

Surviving the Next Pandemic

In the 1918 flu pandemic, a highly infectious bird flu virus emerged and killed 50 to 100 million people. Though that strain died out, many experts are worried that the bird flu virus could again mutate and cause another pandemic.

Pandemic flu is spread just like the seasonal flu: by breathing in respiratory droplets produced when an infected person coughs near you; or by touching an object contaminated by respiratory secretions (a doorknob for example, that was previously touched by someone coughing into his/her hand) and then touching one’s face — eyes, nose or mouth — before first washing or sanitizing hands. (See Natural, Effective Remedies for Colds & Flu for more on protecting yourself.) Both exposures require direct or indirect contact with infected persons, and so the current federal strategy recommends social distancing methods, such as voluntary home quarantine.

This means everyone will be urged to stay home and not venture out to work or school during a pandemic, like we would during a prolonged blizzard or ice storm. Although globally a pandemic may last 12 to 18 months, historically, pandemics have come in waves. In any particular locale, a wave may only last a number of weeks. This is why the Centers for Disease Control is officially calling on all Americans to stockpile 90 days of essential supplies to weather out the next pandemic effectively.

Michael Greger, M.D., is director of public health and animal agriculture at The Humane Society of the United States. This article is reprinted from his exceptional book, Bird Flu: A Virus of Our Own Hatching. You can read the entire book online at here.

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December 2007/January 2008