Intelligence

Avian-flu pandemic 'inevitable'

TheStar.com - Avian-flu pandemic 'inevitable'

DAVID BROWN
SPECIAL TO THE STAR

Robert Webster is watching his long-held hunch about the origin of pandemic influenza play out before his eyes. It would be thrilling if it were not so terrifying.

Four decades ago, Webster was a young microbiologist from New Zealand on a brief sojourn in London.

While he was there, he performed an experiment showing that the "Asian flu" microbe that had swept the globe in 1957 bore an unmistakable resemblance to strains of virus carried by certain birds in the years before.

Webster's observation was a surprise — and a troubling one, suggesting an origin of the unusually virulent strains of influenza virus that appear two or three times each century.

His hunch, that at least some of these pandemic strains were hybrids of bird and human flu viruses, was correct.

Since then, Webster has become arguably the world's most important eye on animal influenza viruses.

These days, he is deeply worried about what he's seeing.

Strains of an influenza virus known as A/H5N1 (the first letter denoting influenza A, an adaptable virus widespread in the animal world) have been spreading in wild and domestic birds across Asia since 1996. In recent weeks, the virus has struck Siberia and Kazakhstan.

Since late 2003, about 100 million domesticated birds — mostly chickens and ducks — either have died of the virus or have been killed to keep the viruses from spreading. But what worries Webster and other experts is that in 112 confirmed cases since 2003, at least 50 people infected with the H5N1 "bird flu" have died — yielding a fatality rate that outstrips any human flu epidemic on record, including the epochal Spanish flu of 1918 and 1919 that killed at least 50 million people.

Webster's insight about the origins of pandemic flu led to an unavoidable conclusion: If scientists had any hope of preventing a pandemic, they had to keep watch on influenza in many species, not just humans.

At 73, Webster heads a team of four principal investigators and a dozen graduate students at St. Jude Children's Research Hospital in Memphis, where the New Zealand native has worked since 1968.

The lab has chambers for handling high-risk pathogens and uses nearly 3,000 fertile chicken eggs a week for growing influenza viruses.

Elsewhere on the St. Jude campus is a small plant licensed by the U.S. Food and Drug Administration to make experimental vaccines. The "seed strain" of virus used to make an H5N1 vaccine now in human trials in the United States was made at St. Jude.

Since 1997, Webster also has spent three months a year as a visiting professor at the University of Hong Kong. That gets him closer to the historical breeding ground of new flu strains: China.

With H5N1 steadily gaining momentum this year, he has returned to Asia twice since his Hong Kong stint ended in March. One trip was to brief prime ministers of the Association of Southeast Asian Nations about what they can to do to stanch the spread of H5N1.

The World Health Organization "will help in the initial outbreak," he says he told them.

"But if it breaks through, guys, you're on your own."

Webster thinks an avian-flu pandemic "is just inevitable. One of these is just going to blow."

For nearly 30 years, he and his colleagues have annually sampled wild ducks in the birds' nesting grounds in Alberta, looking for new flu strains. Since 1985, they have also sampled the feces of more than 5,000 migrating shorebirds along Delaware Bay.

H5N1 strains with slightly different traits have appeared several times in East Asia since the first one emerged in southern China in 1996. Last fall, while analyzing a strain circulating after an outbreak in Hong Kong in 2002, one of Webster's researchers, Diane Hulse, made an unusually important observation.

Many ducks experimentally infected with the virus didn't die, even though the strain was highly lethal to chickens.

But one of the duck viruses was highly lethal to ferrets, the animal whose susceptibility mirrors that of people. This meant that killing infected chickens wasn't going to be enough to stop the spread of the microbe. Ducks could serve as a permanent reservoir of H5N1 virus.

The discovery by Hulse and Webster led in part to an extreme program Thailand mounted last November. About 70,000 investigators went into every village in the country looking for sick ducks and sampling the feces of healthy-looking ones. Flocks carrying H5N1 influenza virus were killed.

The strategy appears to have worked. Last year, Thailand had 12 human deaths from H5N1 flu. So far this year, it has had none.

Stretching out before Webster and public health experts is a long list of chores the world must complete if it is to abort the bird-to-man transfer of disease he long ago proved could happen.

Last month, two teams of scientists based in China, one assisted by Webster, proved H5N1 is now circulating in several species of migratory birds capable of carrying the virus to India, Australia and Central Asia.

A task equal in importance to charting the spread of H5N1 is developing and distributing a good duck vaccine for the billions of those birds in East Asia.

Those countries, which collectively are the likely ground zero of pandemic flu, also need to improve their disease surveillance. In particular, they need to develop laboratories capable of safely isolating and testing influenza viruses.

And while they are doing that, they — and the rest of the world, Webster believes — would be well advised to draw up a plan to limit human movement and distribute vaccine and antiviral drugs should a pandemic flu strain emerge despite the efforts to prevent it.

It's a long list with an uncertain deadline, and it's enough to keep Robert Webster at work.

Washington Post

August 28, 2005 at 10:45 AM in Flu pandemic watch | Permalink | Top of page | Blog Home