An outbreak of avian flu, perhaps the deadly and highly contagious H5N1 strain that has killed poultry in Southeast Asia, Turkey, Romania, Greece and Russia, strikes a North American poultry farm. A threat to the population? No, says Cornell University veterinarian Benjamin Lucio, who keeps a careful watch on poultry in New York state. He is, he says, not overly worried about the virus spreading to humans.
That's because the situation in North America is very different from that in Asia, and Lucio believes that numerous and effective controls are in place to wipe out the virus from poultry populations as soon as it is detected.
In Asia, the H5N1 flu strain has spread widely, mainly through small, unregulated backyard poultry operations, in open markets where infected birds come and go and where people handle infected birds and meat. As recently as this week, the World Health Organization confirmed new cases of H5N1 avian influenza infecting humans -- a father and son in Thailand, and a four-year old boy and a young man in Indonesia. These countries, including Vietnam, have not had the economic means to swiftly counter the spread of the disease.
But, the diagnostic system in place in the United States, Canada and Mexico is certain to detect any virulent avian flu infection in poultry, according to Lucio, who is director of Cornell's College of Veterinary Medicine Avian Disease Program and the university's poultry extension veterinarian. Lucio's job is to diagnose and control avian diseases -- including any form of avian influenza -- in poultry. He surveys commercial farms, backyard operations and pet birds and collaborates with the New York State Department of Agriculture and Markets to keep tabs on live bird markets in New York City.
Because of this close surveillance he is confident that "we will not miss avian influenza, particularly the highly pathogenic variety" that kills birds within a day or two of infection. "Of course, the communication with poultry producers is of paramount importance, but highly pathogenic avian flu is not something you miss. That's because of the dramatic presentation of the disease and the extremely high and sudden mortality," he says. "Once we are alerted by observant poultry producers, North America has the means to detect it and the means to eradicate it."
Even though the potential is there, Lucio is less concerned than some other experts about the possibility that avian flu in its present form will infect humans in North America. In Asia, to date, of the some 120 people who have been hospitalized for avian flu, about 60 have died.
"If you see the numbers of people who have been infected by this virus, it's extremely low," says Lucio. "And I'm sure that the number of people that have been exposed to it is very high." He added that many people would have been in contact with infected chickens through moving, killing and dealing with them in markets and by being involved in eradication campaigns.
"The number of people exposed to avian flu in Asia is probably in the thousands," he says. In the last 10 years in North America, authorities have rapidly contained poultry infected with avian flu of both low and high virulence. There is reason to believe, he says, that there will continue to be swift reaction to contain any highly pathogenic avian flu in poultry, minimizing human exposure.
"The concern would be if -- but that's a big if -- the virus starts transmitting from human to human, because you cannot control movement of people," says Lucio. Fortunately, he points out, in North America, officials can control movement of birds and minimize risks of the virus spreading.
Lucio monitors large commercial farms that hold up to a million birds, as well as smaller backyard operations that raise "free-range" chickens, with 10 to 20 to several hundred chickens raised on grass. He advises both commercial and free-range producers in New York to call Cornell whenever birds die. Farmers can arrange to ship dead birds to the Cornell Animal Health Diagnostic Center, where cause of death can be determined. Lucio also travels regularly to farms around New York state when shipping of dead birds is not possible or the nature of the disease indicates a serious problem.
If avian flu was diagnosed in a poultry flock , the infected poultry would then be killed promptly in a humane manner, using carbon dioxide, which causes birds to lose consciousness and die.
The risk of bird flu infection in commercial farms is lower than in smaller operations because of enhanced housing and biosecurity. Commercial operations are electrically lit and ventilated and completely enclosed, so poultry have no contact with migratory birds. Pastured, smaller flocks have a higher risk of infection because they could mingle with wild migrating birds carrying the virus. So far, Lucio has not detected the avian flu virus in a pastured bird in New York state.
Animal health officials are always on the lookout for any H5 or H7 strains of avian flu virus, because these are the only types that can potentially mutate and become deadly for poultry.
New York City's live bird markets are the main centers where the low-pathogenic H7 influenza virus has been regularly detected. This virus was isolated as recently as last month. On the other hand, H5 strains have not been seen in New York bird markets since 2002, notes Lucio.
Since the low-pathogenic virus is limited to the respiratory tract and intestine, and the virus does not infect humans, the meat of such infected birds can be sold. The highly virulent strains, on the other hand, infect the animal's muscle and tissue and the entire bird must be destroyed to prevent spread to other poultry.
This is the fourth of five articles in the Chronicle Online series detailing Cornell researchers' roles in the global battle against avian flu.