Photograph by Katie Brady, Creative Commons 2.0
Photograph by Katie Brady, Creative Commons 2.0
The Plate

Viruses and Losses: The Global Reach of Bird Flu

To the degree that you think about influenza, it is probably because it is a bad flu season now, and you are either feeling smug that you got the shot, or wondering whether you should have. But there is a larger context for flu that affects the food world—and right now, flu is creating significant disruptions in international trade in food.

China has placed a hold on any imports of poultry or eggs from the US, a trade channel worth more than $270 million per year, because a particular strain of flu has been found in backyard poultry and wild birds in several Pacific Northwest states and in Canada. China is a large poultry-export market for the US, but in blocking trade because of the virus it has a lot of company: about 20 countries have imposed such bans so far.

The Animal and Plant Health Inspection Service (APHIS), part of the US Department of Agriculture, says that the virus has not yet been found in commercial poultry. But because it is so lethal to chickens—it can rip through a flock in days, and the only remedy is to kill the flock to halt the spread—Chinese authorities are being cautious. (And maybe also strategic. More on that later.)

A little vocabulary lesson on flu, to make sense of what comes next: Flu affects humans, but there are also families of strains that naturally affect other animals such as pigs and birds. Avian influenza, or bird flu for short, occurs naturally among wild waterfowl, especially ducks, and spreads across the globe as they migrate. When those viruses cross to other birds, such as chickens, they can cause mild disease and decreased productivity, or they can be lethal. The mild-disease types are known as low-pathogenic, and the lethal ones as highly pathogenic; so, LP or HP. Flu virus strains are also classified by variations in two proteins that occur on the surface of the virus and assist it attaching to cells and causing infection; one is called hemagglutinin (H) and the other neuraminadase (N). (If you’d like to know more, here’s a good explainer from the Centers for Disease Control and Prevention.)

So, now that you can read a flu bulletin, here is the background: In December, agricultural authorities in Canada picked up that a highly pathogenic bird flu strain had erupted on poultry farms in British Columbia, either killing or causing the destruction of more than 250,000 birds. That alerted US federal authorities, who already conduct routine surveys for bird flu, to begin looking in the Pacific Northwest states for any viruses that might have flown across the border. In the middle of the month, they found it: two strains, HPAI H5N2 and H5N8, in wild ducks and in a captive falcon that had been fed meat from wild ducks and had died.

In the ensuing month, the same virus strains were identified in backyard poultry flocks in Oregon, Washington, and most recently in Idaho. Several small flocks have been euthanized. And commercial poultry raisers are hardening the biosecurity in their barns, and watching tensely to see whether the virus crosses to any commercial poultry, as it did in Canada.

If it does, the losses can be devastating. In 2004, a highly pathogenic strain that invaded Canadian farms caused the federal government to kill 17 million chickens.

Fear of such economic loss promoted the Chinese ban, but other fears as well. Highly pathogenic avian flu is notorious for occasionally sickening humans, and causing devastating infections when it does. In 1997, a strain of high-path bird flu that had never been seen before, called H5N1, infected 18 people and killed six of them in Hong Kong, prompting the Chinese authorities to kill every chicken in the city and surrounding area to quell it.

Though they succeeded in slowing the virus down, it subsequently began moving across the world. Since then, according to the World Health Organization, the virus has landed in 16 countries—sometimes in wildfowl, sometimes via smuggled birds— and has sickened 694 people. More than 400 of them have died, a 57 percent mortality rate. The worst influenza epidemic in history, the 1918 “Spanish flu,” began as an avian virus, and killed possibly 100 million people around the world.

The irony in the China ban in particular is that the Chinese mainland is the historic home of new flu strains. Multiple studies over years have demonstrated that new strains emerge as migrating waterfowl congregate on lakes in China; the birds subsequently carry those strains around the globe. But while there are legitimate public health concerns behind the bans, there is economic maneuvering too. As this story from the Economic Times of India illuminates, the US and other countries engage in intense price battles around poultry meat exports. Meanwhile, countries that currently buy live breeding stock from the US are trying to build up breeding industries of their own, and a temporary interruption of the flow of US breeding birds might boost that effort.

At the moment, there is no indication that the avian flu outbreaks in the Pacific Northwest will become a major human health concern. But they bear watching. They are a useful reminder that animal and human health, and national economics and international business, are all linked, around food.