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Worries grow over spread of bird flu

World health officials fear that the bird flu now killing mostly chickens in Southeast Asia will combine with the flu usually infecting humans creating an unstoppable super-strain. NBC's Robert Bazell has details.

Health officials in Vietnam were killing thousands of chickens Friday — as many as they could incinerate.  The country is trying to control an epidemic of bird flu that experts see as a major potential threat to people. The illness has also struck South Korea and Japan.

“This virus seems to be spreading throughout Asia,” said Dr. Richard Webbe of St. Jude Children’s Research Hospital.

The World Health Organization confirmed Friday that a fourth person in Vietnam had died from the bird flu. At least 15 other deaths there are suspected, but those cases are not the major cause for concern.

The reason the bird flu is so potentially dangerous is that different strains of the influenza virus are able to combine their genetic material. The fear is that the bird flu, which is now killing mostly chickens, will combine with the flu virus that usually infects humans and create an unstoppable super strain.

The World Health Organization is carefully watching for any evidence of person-to-person spread of the bird flu. So far it has found none.

“If we had one of these bird flu viruses that transmitted human to human, the SARS epidemic would be very, very trivial,” said Dr. Robert Webster, also of St. Jude Children’s Research Hospital.

From chickens to pigs
In one ominous development, Vietnamese officials say the virus is spreading from chickens to pigs and among pigs.  Experts say that makes it more likely that a form that is dangerous to humans could arise, leading to a global pandemic.

“Any outbreaks where we see pig involvement we get concerned about,” added Webbe.

Scientists are also concerned because outbreaks of bird flu in which people die are becoming more frequent.

“The reason why we see this interspecies transmission is the simple fact of population density, the density of animals to feed the population, increasing the standards of living throughout the world. More people want to have protein, so you have more chickens, you have more pigs and you have more people,” said Webster.

A combination, experts say, that puts the world at risk for a dangerous new strain of flu.