Bird Flu: A Virus of Our Own Hatching

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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:

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