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Top flu expert warns of a swine flu-bird flu mix

(Agencies)
Updated: 2009-05-08 17:16

MEXICO CITY -- Bird flu kills more than 60 percent of its human victims, but doesn't easily pass from person to person. Swine flu can be spread with a sneeze or handshake, but kills only a small fraction of the people it infects.

So what happens if they mix?

This Aug. 16, 1957, file photo of Dr. Joseph Ballinger giving Marjorie Hill, a nurse at Montefiore Hospital in New York, the first Asian flu vaccine shot to be administered in New York City. [Agencies]

This is the scenario that has some scientists worried: The two viruses meet -- possibly in Asia, where bird flu is endemic -- and combine into a new bug that is both highly contagious and lethal and can spread around the world.

Scientists are unsure how likely this possibility is, but note that the new swine flu strain -- a never-before-seen mixture of pig, human and bird viruses -- has shown itself to be especially adept at snatching evolutionarily advantageous genetic material from other flu viruses.

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"This particular virus seems to have this unique ability to pick up other genes," said leading virologist Dr. Robert Webster, whose team discovered an ancestor of the current flu virus at a North Carolina pig farm in 1998.

The current swine flu strain -- known as H1N1 -- has sickened more than 2,300 people in 24 countries. While people can catch bird flu from birds, the bird flu virus -- H5N1 -- does not easily jump from person to person. It has killed at least 258 people worldwide since it began to ravage poultry stocks in Asia in late 2003.

The World Health Organization reported two new human cases of bird flu on Wednesday. One patient is recovering in Egypt, while another died in Vietnam -- a reminder that the H5N1 virus is far from gone.

"Do not drop the ball in monitoring H5N1," WHO Director-General Margaret Chan told a meeting of Asia's top health officials in Bangkok on Friday by video link. "We have no idea how H5N1 will behave under the pressure of a pandemic."

Experts have long feared that bird flu could mutate into a form that spreads easily among people. The past three flu pandemics -- the 1918 Spanish flu, the 1957-58 Asian flu and the Hong Kong flu of 1968-69 -- were all linked to birds, though some scientists believe pigs also played a role in 1918.

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