Will Bird Flu Fly Into Our Lives?
Federal and state biologists have launched a massive new monitoring program designed to determine whether wild migratory birds are bringing a deadly virus into North America
SCORES OF BIOLOGISTS took to the field last summer at more than 50 sites in Alaska, netting and examining thousands of migratory birds belonging to 27 species. The biologists also examined birds killed by hunters. The Alaska project was part of a nationwide effort to collect up to 100,000 samples of various kinds from dead and living migratory birds all over the United States—the largest wildlife disease surveillance program ever launched in North America. The goal: to determine if a highly lethal form of Old World bird flu is making its way into North America.
At a cost of $29 million in 2006, the Interagency Plan for Early Detection team—composed of biologists from the U.S. Department of Agriculture’s Wildlife Services division, the U.S. Fish and Wildlife Service (FWS) and state wildlife agencies—took its work to all 50 states. The flu virus they sought bears the unwieldy name “highly pathogenic avian influenza H5N1” (HPAI H5N1). The H5 and N1 refer to two different proteins that occur on the surface of the virus and that identify it.
Low pathogenic avian influenza viruses are common and generally do not sicken wild birds. However, H5N1 has killed wild birds by the thousands and has infected domestic flocks, resulting in the death of more than 200 million chickens in Europe and Asia. What scientists find most alarming is the disease’s unprecedented ability to infect humans directly from poultry.
Bird flu first appeared as a human health threat in Hong Kong in 1997, when it infected 18 people, six of whom died. All had been in close contact with infected domestic poultry. “Historically, there have only been a handful of human infections from an avian influenza virus,” says Tom Roffe, FWS chief of wildlife health. “Most of these have been asymptomatic. Along comes HPAI H5N1 with over 230 infections and 100-plus mortalities. So, now we know this virus can infect people, although not very easily.”
The ease of transmission to humans could change, however, if a person infected with human influenza virus is exposed to HPAI H5N1. The two viruses could exchange genetic material, potentially giving the bird flu the ability to spread easily among people. “Then you’re primed for the next pandemic,” Roffe says. “That’s what has people worried.”
Controlling the spread of the flu among domestic birds is relatively easy, as domestic stock can be killed to contain infections. Wild birds pose a more difficult challenge. “There would be no way to ensure capture and removal of most, or even many, of potentially infected wild birds,” Roffe says. “Wild birds simply fly away further, spreading the virus. Even if removing potentially infected birds were possible, we have no clear understanding of what benefit, if any, that might bring.” H5N1 presently is limited to Asia, Africa and Europe, but disease specialists fear that migratory birds could carry the virus into North America. “Wild birds usually contract avian influenza viruses by eating or drinking contaminated food or water or from respiratory secretions and fecal droppings,” says Tom DeLiberto, national wildlife disease coordinator at the U.S. Department of Agriculture in Fort Collins, Colorado.
The federal government launched its multiagency study last summer to assess the wild bird risk by capturing migrants and testing them for the disease. “It’s clear wild migratory birds can carry HPAI H5N1 and have been shown in isolated cases to transmit it back to poultry, but we don’t know if they are major or minor players,” Roffe says.
The study began in Alaska, where more than 40 species of migratory birds from Asia share habitat with North American birds. Millions of these birds fly from Alaska into the Lower 48 each fall. The interagency team captured some 19,000 birds in Alaska last summer to collect tracheal and cloacal samples. They also are analyzing water and soil samples from wetlands.
The 27 species on which the Alaska part of the program focused included 13 of particular interest, such as horned grebes, dunlins, red knots, buff-breasted sandpipers and various waterfowl, such as tundra swans, greater scaups and northern pintails. “We picked our biggest risk area and our most usual movement patterns, because the chances are that we’re more likely to find [the flu] there,” Roffe says. “But there’s nothing to say that it couldn’t show up in New Jersey first.”
Indeed, New Jersey state wildlife officials and those in other states, along with federal biologists, are monitoring migratory birds across the nation as fall flights involving more than 100 million birds head south. “We know there are lots of pathways by which this virus can move,” Roffe says.
If HPAI H5N1 is found in wild migratory birds in the United States, scientists will expand surveillance efforts in the area where they found the flu, follow the infected bird species’ historical flight routes to anticipate where the virus may show up next and increase bio-security measures at commercial and noncommercial poultry operations in those areas. Hunters, wild-bird rescuers, bird-watchers and others will be notified of potential risks and safety precautions, such as avoiding contact with sick birds, properly handling and cooking wild birds, practicing good sanitary practices after handling birds and reporting sick or dead birds to local authorities.
“It’s important to note that the detection of HPAI H5N1 in wild birds does not signal the start of a human flu pandemic,” DeLiberto says. “This is still a disease among birds, not people.”
Utah-based writer Marilyn Stone covers hunting, wildlife disease and conservation issues.
Movements and Monitoring of Bird Flu
- First viral outbreak of HPAI H5N1 reported in Hong Kong: 1997
- U.S. Department of Agriculture starts monitoring for the virus in wild migratory birds: 1998
- Virus arrives in Korea as a major outbreak in chickens: 2003
- Reports of the virus in Japan, India, Indonesia and other Asian nations: 2004
- Russia, Mongolia, Turkey, eastern Europe and Italy report the virus; U.S. Department of the Interior begins working with Alaska wildlife agencies to test wild migratory birds: 2005
- Virus is found in Egypt and other African nations and in western Spain; state and federal wildlife agencies in the United States launch effort to collect 100,000 wild migratory bird samples nationwide in early-detection program: 2006
Key Migratory Birds Tested in Massive Flu-Detection Effort
These 13 birds, of 27 being monitored closely in a new federal and state cooperative program, are of primary interest for early bird flu detection. Their migratory patterns place them among birds most likely to bring avian flu into North America.
Lesser sandhill crane
Lesser snow goose
Pacific golden plover
Good Flu News
Key to concerns about a possible global epidemic caused by the highly pathogenic bird flu known as H5N1 is the ease with which the virus can pass from bird to human. On that front, science has recently produced some welcome news.
A recent study by researchers from the World Health Organization, the United Nations Food and Agricultural Organization, the U.S. Center for Disease Control and other entities has concluded that the H5N1 bird flu virus may not transmit easily from bird to human.
Conducted in a Cambodian village in which a 28-year-old man infected with the virus had died in March 2005, the study surveyed 351 people from 93 households living within two-thirds of a mile of the victim’s home. Despite regular, close contact with birds that researchers suspected of having H5N1 infections, none of the people interviewed showed any indication of having had the disease.
The study suggests that people who fall ill may simply be more susceptible than others or have physical conditions that predispose them to the illness. “This study also provides evidence of the low transmissibility of the H5N1 virus from infected poultry to humans, even in circumstances in which human/poultry interactions are regular and intense,” the study concluded.—Roger Di Silvestro