It's not just the nation's hospitals, coroners and clinics that are keeping an eye out for signs the deadly avian flu has reached U.S. shores, but zoos as well.
With a controlled population of birds and animals under constant watch by experts, zoos make great listening posts for illnesses like avian flu.
"We are very good canaries in the proverbial coal mine," said Dr. Dominic Travis, director of the Davee Center for Epidemiology and Endocrinology at the Lincoln Park Zoo in Chicago. "But we're better than that because we can also help solve the problem."
Zoos have helped detect and deal with past deadly disease outbreaks.
Back in 1999, Dr. Tracey McNamara, a veterinarian at the Bronx Zoo, was investigating the mysterious death of a number of wild crows found on zoo grounds.
After some testing, investigation and analysis, McNamara concluded it was the rare and deadly West Nile virus that had killed the birds -- and a number of New Yorkers too.
"They [the Bronx Zoo] were the first ones to connect the bird cases and human cases," said Dr. Nina Marano, associate director for Veterinary Public Health at the CDC. "This wasn't part of their protected species, but because they represent a great place for urban wildlife to reside thanks to their being very attractive places that have ponds and trees, wildlife flock there."
City zoos have often played host to local bird and animal populations just looking for a patch of green to call their own.
Since the zoo's staff monitors and tests its population, it becomes an ideal sentinel on the lookout for new illnesses.
"We have a lot of different species that are susceptible to these things, we have keepers that are well-trained in husbandry and health," Travis explained. "We have vets available that can deal with the next level of health and take samples and are prepared to deal with the testing and then the response to that, and we have millions of people coming through the gate so we represent places of congregation."
Their experiences with West Nile may help them better prepare for the next outbreak.
"What we've learned from West Nile and some of these other emerging pathogens is that the emerging pathogens don't necessarily read the book and what we might think or predict can happen is going to take might not," Marano said. "We might be very surprised where the first case is actually detected and in what form, what species it will be detected at."
After the West Nile cases were identified, the American Zoo and Aquarium Association began coordinating with public health agencies like the USDA and CDC to develop plans that would include them in the surveillance of epidemics.
In 2003, an outbreak of "exotic Newcastle disease" in Southern California offered the San Diego Zoo and the national zoo community a valuable lesson on how to deal with a dangerous disease whose targets are not dissimilar from avian flu.
Exotic Newcastle disease is a viral infection that can quickly kill entire flocks of unvaccinated poultry.
"The disease is highly contagious among birds, and causes a high mortality in poultry particularly, but in all bird species," said Dr. Don Janssen, a veterinarian with the San Diego Zoo. "We got a lot of experience because of that disease in protecting our collection from diseases that are highly contagious in birds."