In mid-February, the owners of a backyard flock in Suffolk County, NY, noticed two guinea hens and three of their chickens were sick. Three days later, the birds were dead. Within five hours of getting a swab of the birds’ airways, the New York State Veterinary Diagnostic Laboratory determined it was New York state’s first case of a deadly strain of avian influenza.

Cornell researchers knew highly pathogenic avian influenza, or bird flu, was coming. They had been tracking the disease’s spread for months. “We knew how to implement strategies to prepare, and prevent potential losses,” says anatomic pathologist Gavin Hitchener, director of Cornell’s Duck Research Laboratory, located 15 miles from the backyard flock.

Hitchener and others at the Animal Health Diagnostic Center (AHDC), part of the Cornell University College of Veterinary Medicine (CVM), have been helping to keep New York’s avian flu incidents remarkably low through education, outreach and testing measures. As of April 6, the state has had only one outbreak in a small commercial flock and seven in backyard flocks. So far, all of the state’s large commercial operations have remained unscathed.

What is bird flu and why can it be so devastating?

“Because backyard flocks are usually outside, free-range, they’re mixing and mingling with migratory birds. They may pick the virus up from the feces of wild birds in their environment,” says veterinarian Jarra Jagne, DVM ’90, head of the Animal Health Diagnostic Center’s Avian Health Program and associate professor of practice in the Department of Public and Ecosystem Health at CVM.

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There are 144 types of avian influenza. Some cause just mild respiratory infection. But the current strain, H5N1, is highly pathogenic and causes extreme mortality, says Jagne. When the virus takes hold, it replicates rapidly in the respiratory, neurologic, digestive and reproductive organs. “It is systemic–throughout the whole body. This virus just enters and destroys the tissues,” Jagne says. “Within 24 to 48 hours after seeing the first sick or dead birds, you will see very high mortality.”

Waterfowl, like geese and gulls, are the natural reservoirs of all avian influenza. Other wild birds can be infected, such as bald eagles, owls and other birds of prey, says Krysten Schuler, director of the Cornell Wildlife Health Laboratory. “A lot of birds of prey–eagles and vultures–were affected, because they scavenge dead birds,” she says. “And we have seen the virus too in some mammals.”

Because it is so devastating, “high path avian influenza is at the top of the list” of diseases the center tracks, says AHDC’s executive director François Elvinger, professor of population medicine and diagnostic sciences and associate dean for diagnostic operations and government relations at CVM.

The Cornell team will continue their efforts to keep the number of cases low as the fall migration ramps up, Jagne says. “We’ve been spreading the word: If you see any mortality, or unusual mortality, in your flock, give us a call.”