(Agencies)
Updated: 2004-02-26 11:32

Scientists should have a better idea soon of the chances of bird flu combining with a human strain to create a feared new mass killer, a top World Health Organization official said on Wednesday.

Under high security, researchers in laboratories in the United States and Japan will begin mixing the avian virus ravaging poultry in Asia with the common and highly contagious human variety to see what they produce.

Flu viruses get together readily, that is how they change and survive, but what nobody knows yet is what are the most likely combinations to emerge from such a marriage and just how dangerous they could be to humans.

"By the end of April...we may have a better understanding of that question," said Klaus Stohr, chief influenza expert at the World Health Organization (WHO).

The human death toll stands at 22. But health officials fear that it could yet trigger a worldwide pandemic, possibly even rivalling that of 1918 when some 40 million people died, if the deadly, but so far not very infectious bug "mates" with a quick-spreading human type.

It has been 35 years since the last flu pandemic, also triggered by a strain jumping the species barrier from animals, and scientists have long warned that another is overdue.

MIXING BOWL

Stohr said that the laboratory work on mating the viruses was just one of three lines of investigation the WHO had set in motion to improve understanding of the health threat.

Scientists in Amsterdam were using monkeys and ferrets, whose susceptibility to flu is similar to a human's, to study how the avian virus affects people, notably which parts of the body it reaches and when the immune reaction begins.

Knowing whether the virus stays in the lungs or reaches the brain or the liver would influence decisions on the type of antiviral drug to use in the event of a big outbreak, Stohr said.

Scientists had been unable to carry out autopsies on many of those killed by avian flu in Thailand or Vietnam to gain such information because of resistance from relatives, he said.
Other research involved pigs, whose lungs appeared able to house both human and avian flu viruses and so provided an ideal "mixing bowl" for the two, he added.

Once the U.S. and Japanese laboratories had identified the new strains most likely to be created from any marriage, the next phase would be to test these prototypes on ferrets to assess how dangerous and infectious they were.

"This should help us understand how quickly we would have to move (in getting ready). If it is highly transmissable and doing a lot of damage, we are going to have to redouble our efforts," he said.

This work would require the top international bio-security rating -- BSL4 -- which is used for the most deadly pathogens in order to shield the scientists, who must wear full-body protective gear, and to guard against any leak.

"There are always risks," said Stohr, when asked about the chance of a new superbug escaping the laboratory. "But I believe that the risk is manageable."