Avian flu found in migrating geese in China

The spread of a highly lethal strain of avian flu to thousands of migrating geese in China is stirring concerns among disease trackers that the birds could transport the virus to vast new swaths of the world, with the potential of igniting a long-feared global influenza epidemic in humans.

Chinese scientists yesterday, in articles in the journals Nature and Science, described the sudden deaths of bar-headed geese in recent months at a sprawling saltwater lake in the western part of the nation. It marked the first time that avian flu, which had proved deadly mainly to poultry in the past, has killed big flocks of migratory birds, with at least 6,000 dying so far.

Already, scientists are drafting plans to track the movement of the geese from China and into India and elsewhere in South Asia. There, the waterfowl could cross paths with birds winging their way from Europe in coming weeks.

Since 1997, when avian flu first struck humans, disease specialists have watched with growing unease as an especially infectious strain of the virus felled poultry in Southeast Asia and sickened humans. In the past two years, bird flu has infected 108 humans, killing 54, who suffered severe respiratory complications.

And those human cases gave birth to an even more foreboding scenario: The bird flu could meld with human influenza strains and spawn a super bug capable of being spread person to person -- so mighty it could wipe out millions.

''That is what we have all been fretting about for so long -- that this is the spark that would set off the forest fire of a pandemic," Dr. William Schaffner, a flu specialist at Vanderbilt University, said yesterday in a telephone interview.

Now, the Chinese scientists report, the discovery of bird flu in geese capable of covering hundreds of miles a week could signal that the virus has found a vehicle to spread far and wide -- and swiftly.

''We do know that if this virus continually expands its distribution even farther, this means much more human population will be exposed to this virus," said Yi Guan, an author of the Nature report and bird flu specialist at the University of Hong Kong. ''In India or Bangladesh, these birds have the opportunity to meet birds from Europe. If this virus circulates among them, who knows? Next year, maybe the birds come back to Europe with this virus. This is the nightmare for the world."

While scientists expressed deep concern about the emergence of avian flu in migratory birds, they also acknowledged that at the moment it is impossible to gauge exactly how much danger the fowl pose to humans. In the past, the virus has been transmitted to humans through close contact with infected poultry.

In telephone interviews this week from China, authors of the reports conceded the virus could, for example, burn itself out within the infected flocks, with contagious birds dying before they could transport the virus elsewhere. Or the waterfowl that survive the infection could turn out to be efficient carriers of the virus.

''Will the birds carry the virus? Will the virus fly to places like India? At this point, we can't say," said George F. Gao, a microbiologist at the Chinese Academy of Sciences and an author of the report in Science. ''But we can't rule out this possibility."

Because the stakes are so substantial, Guan recommended urgent actions to contain the spread of avian flu among waterfowl and to monitor their travels as they soar across the Himalayas in late summer, bound for South Asia. In the past, when bird flu has swept chicken flocks, millions of birds were slaughtered to prevent further spread.

The tracking, Gao said, will probably consist of collecting fecal droppings from the birds and analyzing their contents for the presence of a particularly dangerous strain of bird flu known as H5N1.

Dr. David Ozonoff, a Boston University professor who has studied the flu, said even more aggressive measures are warranted to follow the birds, including placing bands on them that would track their progress. Even so, Ozonoff said, there's no real hope of being able to contain the movement of the waterfowl.

''What can you do?" said Ozonoff, a professor of environmental health at BU's School of Public Health.

''These are wild birds flying all over the place. The genie is out of the bottle. I just don't see that there's much that can be done about this."

In late April and early May, a scattering of dead birds was discovered on islands in Qinghai Lake in western China. In the Nature account, scientists report that by May 4, birds were dying at a rate of 100 a day.

By this month, Guan said, the count of dead geese and gulls had grown to 6,000.

Avian flu had been found in migratory fowl before, but, in most cases, it didn't appear to make the birds ill. And when they did become sick and die, they typically were found adjacent to poultry farms where the virus continues to circulate.

The mass deaths in Qinghai Lake, a secluded nature reserve far from any chicken farms, were a disturbing anomaly, scientists said. Somehow, the virus had made subtle changes in its genetic clothing -- changes that allowed the birds to spread the germ to each other.

That caught the attention of health agencies that have been warning about the potential of a flu pandemic, which could claim millions of lives and overwhelm medical systems.

In their accounts, the Chinese scientists document that genetic alteration: The virus extracted from the dead birds, they reported, belongs to the same family as the form of H5N1 that has killed humans in Southeast Asia, but is not a twin.

Further analysis showed that its genetic profile is similar to a virus found in poultry in southern China, leading to suspicions that the waterfowl contracted the infection from chicken.

The implications of the genetic shift in the H5N1 virus are unclear, scientists said. They cannot say whether it might pose more of a threat to humans or less, but they do know it is sufficiently similar to the virus infecting humans that it bears watching.

''I think it would be very, very foolish and imprudent to think that something worse couldn't happen," Ozonoff said.

Stephen Smith can be reached at stsmith@globe.com.