If avian influenza spreads to Hawai'i, it likely will arrive on the wings of a Pacific golden plover or some other migratory bird returning from arctic nesting grounds.

Once here, the disease could spread to backyard pens, poultry farms and the clusters of feral chickens that roam many communities. It could impact operations at the Honolulu Zoo and wildlife refuges, threatening native birds already teetering on the brink of extinction.

Evidence is mounting that wild birds may have been the source of recent outbreaks in China, Russia, Central Asia, Europe and Africa. Hawai'i wildlife officials are working to develop a monitoring strategy in time for the start of the migratory season in August, when birds arrive here at wetlands and large open spaces.

Avian influenza, also known as AI or bird flu, is a contagious disease caused by viruses that normally infect only birds. A less potent form of the disease triggers mild symptoms in birds, such as ruffled feathers, but the highly virulent H5N1 strain can spread rapidly through poultry flocks, with near 100 percent mortality.

On rare occasions, the disease has crossed the species barrier, at last count infecting 177 people and killing 98 in Cambodia, China, Indonesia, Thailand, Turkey, Iraq and Vietnam since 2003. The virus is carried in bird feces, and the main route of human infection has been direct contact with infected poultry or contaminated surfaces and objects.

Most worrisome to health officials is the possibility the virus will mutate into a form that is highly infectious for humans and will spread easily, triggering a global outbreak that could kill millions.

The consequences of a bird flu pandemic for Hawai'i could be devastating, not only in terms of the health and environmental impacts but in economic losses, as tourists avoid known flu hotspots, as they did during the SARS scare.

"I can't predict how it's going to come here or whether it will come here before its introduction by humans," said Duane Gubler, director of the Asia-Pacific Institute of Tropical Medicine and Infectious Diseases. "The fact that you have Asian birds perhaps most likely mixing with birds that come down across the Pacific is a good indication it could be introduced by migratory birds. It's a major, major concern.

"With the state quarantine on importing poultry, that's less likely."

The institute is part of the University of Hawai'i's John A. Burns School of Medicine in Kaka'ako. Gubler said the task for public health officials worldwide is to contain avian influenza in the bird population before it can make the jump to humans.

"The challenge is that it is such a 'hot' virus," he said. "It emerged in Asia and has spread through Asia and around the world. The only place it hasn't been detected is in the western hemisphere, and that's most likely just a matter of time."

In fact, officials worry the virus could arrive in North America with the spring bird migration to Alaska.

ON ALERT

Avian flu surveillance in the migratory bird population has become a priority for federal wildlife agencies. The U.S. Geological Survey's National Wildlife Health Center in Honolulu is working with federal and state partners to monitor migratory birds here and elsewhere in the Pacific. Simultaneous efforts are under way in other regions with migratory ranges that connect to bird flu zones.

Thierry Work, a USGS wildlife disease specialist, said the center has been doing necropsies on dead migratory birds to test for disease and is working with other organizations to set up a system for taking samples from live birds.

"Little is known about migratory bird patterns in Asia," Work said. "We are devising a way to do surveillance of live birds, especially with priority species like Pacific golden plovers, wandering tattlers, sanderlings and other birds known to migrate from Alaska to Hawai'i, but also probably from the Pacific islands and other places in Asia."

A federal surveillance plan calls for sampling at least 200 individuals from each species, but Work said that in Hawai'i, migratory birds are widely dispersed and seldom group together in large flocks, so obtaining the required number of samples could be difficult. The birds would be trapped, marked and released after samples are taken using swabs.

A report prepared by a newly formed working group on the avian influenza threat to Hawai'i and other Pacific islands recommends hiring and training additional staff for bird surveillance, and that Hawai'i establish a laboratory to provide rapid testing of samples for the H5N1 virus. Samples are now sent to mainland labs in a process that takes several days.

Gubler said a grant is being sought from the National Institutes of Health to set up such a facility at the UH medical school.

Biologists also are seeking money to study the movement of birds between the Pacific and Asia and the North American tundra and Siberia, according to wildlife biologist Fern Duvall of the state Department of Land and Natural Resources' Division of Forestry and Wildlife.

He said more than 40 species of birds that have been spotted in Hawai'i over the years are known to migrate to the North American arctic, where they could mix with infected birds from Asia. There also are a handful of species that migrate in small numbers directly from Russia and Kazakhstan, where avian influenza has been detected. These include the sharp-tailed sandpiper and white-fronted goose, Duvall said.

"It's a small number, not anything like the 250,000 geese that show up there. ... But people don't know" the extent of the direct migration, Duvall said.

Some experts theorize that Hawai'i's remote location in the middle of the Pacific could provide some protection from the flu because of what Duvall called "the splash-down effect" — a sick bird wouldn't have the strength to fly this far and would splash down in the ocean before reaching the Islands.

But Duvall's not so sure.

"There are long-distance migrations between Asia all the way to Africa, and the virus is starting to show up in those places," he said. "It could also be that some birds, like wedge-tailed shearwaters, have it and do not get sick, but when they pass it on to other birds, those birds die.

"Bird flu is something birds have had for a long time. That the virus is getting more virulent and killing more birds means it is altering and moving and killing birds in many areas," Duvall said. "I think the general professional opinion about the seriousness of the threat is not overblown. It's when it's going to arrive rather than if, and what happens when it gets here."

THE ZOO ZONE

The Honolulu Zoo, which has hundreds of birds, has been part of recent meetings between state and federal agencies to begin coordinating protocols for a potential outbreak.

"We might have to take some drastic steps, such as closing the walk-through aviaries," zoo veterinarian Ben Okimoto said.

The American Zoo and Aquarium Association in November released guidelines for monitoring and prevention of the H5N1 virus. Measures include discontinuing direct contact between visitors and zoo birds, suspending behind-the-scenes tours of animal food preparation and storage areas, and bringing indoors the birds that commingle with free-ranging waterfowl and shorebirds.

"We're thinking about how to take steps to prevent exposure, but it's difficult," Okimoto said, because the zoo is wide open.

DLNR chairman Peter Young said it is not known how avian influenza would affect Hawai'i's fragile forest birds, some of the rarest in the world, since they live in isolated habitats. But he said the disease could be a major threat to native waterfowl such as the koloa, nene and Laysan duck, which share wetlands with migratory species.

Duvall said the virus could spread from wetlands via cattle egrets, which visit areas frequented by waterfowl and shorebirds "then spread out to all over the island during the daytime."

Plans are not far enough along to determine what actions are needed if the H5N1 virus makes landfall in Hawai'i, but Duvall said a strategy could include "targeted work" with some birds.

He said much still needs to be learned about the state's wild and domestic bird populations.

"It's important to intercept the very first appearance of bird flu in Hawai'i," he said. "It's important to know where people have chickens, and where cattle egrets roost."

Work said people needn't fear the kolea (plover) and other migratory birds.

"You need to keep it in perspective. Most of the people infected had intimate contact with domestic poultry. Just because a migratory bird is sick doesn't mean a human is going to get it," he said.

CHICKENS IN THE WILD

The state's wide-ranging feral chicken population also would draw attention with a bird flu outbreak, Young said.

None of the agencies contacted by The Advertiser said they had discussed rounding up the birds as part of a response to an epidemic, and officials said it is not clear who, if anyone, is responsible for feral chickens, since they are not endangered and can be found on private, county, state and federal lands.

The 2002 outbreak of exotic Newcastle disease in the United States prepared the poultry industry for new epidemics such as avian influenza, said veterinarian Jim Foppoli of the state Department of Agriculture. Birds of foreign origin that are imported into Hawai'i are sent first to federal quarantine sites on the Mainland for a 30-day holding period.

Most of the 250,000 day-old chicks imported annually for Hawai'i's egg farms are produced at large corporate hatcheries in Washington state and British Columbia that follow strict biosecurity rules, Foppoli said.

"Nowadays all these flocks are AI-monitored. We don't feel that day-old chicks coming in are of any real substantial risk," he said.

There are roughly 480,000 layers at Hawai'i egg farms and countless others raised in backyard pens. Foppoli said farms of all sizes should become familiar with measures aimed at preventing commingling of domestic and wild birds and the introduction of diseases by contaminated vehicles, equipment and clothing.

Smuggling of pet birds and gamecocks from foreign ports and the import of prohibited poultry products does occur, but it's "so small it's off the radar screen," said Claude Knighten of the USDA's Animal and Plant Health Inspection Service. It's "not a good pathway for avian flu."

Foppoli said that what travelers bring in on their shoes and clothing from AI zones probably is more of a threat than bird imports.