IT MUST SEEM like the sky is falling -- that it's about to rain chaos and death as the dreaded H5N1 avian flu appears to close in.
Last spring, bird flu broke out in Cambodia, Thailand and Vietnam. It spread to western China, Siberia, Kazakhstan and Mongolia in the summer. How did it travel half a continent?
Though maps of the outbreaks show the flu following roads, railway lines and national borders, many flu experts insist that migratory birds spread the virus across Asia. Julie Gerberding, director of the Centers for Disease Control and Prevention, warned that some of the birds might fly to Alaska, then down into the United States, bringing the bird flu with them. That hasn't happened, but the virus appears to be in Europe. Last week, ducks and chickens were found dead in Romania, Turkey and Greece.
News reports make the threat even more ominous. In resurrecting the 1918 pandemic virus, the deadliest flu strain of all time, researchers recently learned that this strain was far deadlier than any other human virus -- it killed mice, while normal human flu won't even ruffle a mouse's fur. They also found out that all of its genes came, directly or indirectly, from birds. Unlike the pandemics of 1957 and 1968, the 1918 version didn't arise from a combination of bird and mammal genes. Instead, the bird genes evolved into a human virus that killed as many as 50 million people.
This means, say breathless news reports, that what happened in 1918 could happen again, this time with H5N1.
But Peter Palese doesn't think so. He is lab director at Mount Sinai Hospital in New York, where the technique that re-created the 1918 genes -- known as reverse genetic engineering -- was developed. He and associate Adolfo Garcia-Sastre contend that what the resurrected virus really shows is how supremely adapted it is -- how well its parts fit together, how perfectly it works. The sublime malignance of the 1918 virus doesn't lie in one part but rather in how the genes function together. Evolution shaped this virus to be a sleek, effective killing machine.
We don't know what bird the genes came from originally. It wasn't a domestic duck, chicken or goose, because their flu strains are quite different. According to Jeffery Taubenberger, the senior researcher at the Armed Forces Institute of Pathology, the 1918 flu originated in an unknown bird reservoir, one equally distant from American and Eurasian birds. "To me, it's from an unknown host, evolutionarily isolated from other birds," Taubenberger said last year.
