October 10, 2005
Monday

When the virus most likely to launch the next global pandemic finally makes its way to North America, the first warnings may come not from doctors or epidemiologists but from an unexpected source: Alaskan duck hunters.

For the past eight years, public health experts around the world have been warily monitoring events in Southeast Asia, where a strain of influenza virus - identified as H5N1, for the variants of two proteins (hemagglutinin and neuraminidase) found on its surface - has shown a propensity to jump the species barrier from birds to humans.

It was just such a trans-species leap, made possible by the remarkable mutability of viral genes, that many researchers believe launched the deadliest global influenza pandemic in recorded history. From 1918 through 1920, that outbreak killed 50 million to 100 million people worldwide, nearly 700,000 in the United States.

The warnings about a possible repeat have apparently grabbed the attention of political leaders, including President Bush, who spoke about the issue at some length during a news conference Tuesday. He even recommended a book on the subject: John Barry's "The Great Influenza: The Epic Story of the Deadliest Plague in History."

Barry's book is a very good reference on the 1918 pandemic, particularly effective in analyzing how an inept government response to the outbreak likely worsened its severity. In the wake of the woeful federal, state and local response to Hurricane Katrina, even Bush's critics can take some comfort from knowing that he's been thinking about how the nation might respond better to a potential public-health crisis of unparalleled magnitude.

Whether that thought leads to better execution of policies and procedures remains to be seen - and Bush is already taking heat for suggesting the military might play a key role in enforcing quarantines and other flu precautions - but admitting the severity of the threat is a crucial first step.

The H5N1 influenza virus historically has been found only in birds, originally wild species but more recently in domestic chickens, turkeys, geese and ducks. Outbreaks among poultry have been reported in China, Cambodia, Indonesia, Malaysia, Thailand, Vietnam, Japan, Laos, South Korea and Kazakhstan.

In 1997, however, H5N1 was found to have infected 18 people in Hong Kong, killing six. Human infections have now been reported in Thailand, Vietnam, Indonesia and Cambodia, resulting in 60 deaths since 2003.

After a virus leaps to humans from another species, it typically does not move easily from person to person because its replication machinery is adapted to a different genome. But once inside a human host, the avian influenza virus is capable of swapping genes with human-adapted influenza viruses.

That new genetic information can enable the mutant to move easily among people, who will have no immunity to the novel invader. There is some evidence that H5N1 may have been transmitted from one person to another, suggesting it is on the verge of acquiring this ability.

The virus has been detected in wild birds in northern Asia, and those birds often migrate across the Bering Strait to Alaska. It is not known whether migratory birds have played a significant role in spreading avian influenza - and epidemiologists consider travel by infected humans the most likely trigger of a global outbreak - but scientists are concerned enough to monitor the possibility.

The U.S. Fish and Wildlife Service, the U.S. Geological Survey, the Alaska Department of Fish and Game, and several public health agencies have established a surveillance project in Alaska intended to detect the presence of the avian influenza virus in migratory wild birds. They've enlisted the help of hunters in tracking suspicious bird deaths, and have issued advice about precautions to prevent human infection.

The surveillance program tested thousands of waterfowl and shorebirds this summer, and more tests are planned next year. So far, the virus hasn't turned up.

There's a nearly poetic aspect to Alaska's potential role as the front line in the next global struggle against influenza. Researchers this week reported in the journals Nature and Science that they had re-created the 1918 flu virus, allowing them to compare its genome to that of the H5N1 virus and providing valuable clues about its lethality, transmissibility and source.

Some of the genetic material used to resurrect the virus was obtained from the body of a 1918 flu victim pulled from an icy grave in the Alaskan permafrost in 1998. It appears, the researchers conclude, that the virus originated in birds.

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