Scientists are embarking on a raft of experiments with the bird flu virus ravaging Asian poultry stocks to see how dangerous it could be if it adapted to humans.
Researchers will mix the virus with a normal human flu variety to see how well they swap genes. They also will engineer various combinations of the two viruses to test which mutants would be the most hazardous, said Klaus Stohr, chief influenza expert at the World Health Organization in Geneva, which is coordinating the tests.
Research on monkeys and other animals is designed to help scientists understand how a pandemic strain based on the Asian bird flu would behave in humans.
"What we want to do is reduce surprises. Every surprise will cost lives," Stohr said in a telephone interview. "We still have the time here to do the research. We don't have much time, but the pandemic isn't there yet."
The avian influenza outbreak has forced the slaughter of more than 80 million chickens and other fowl in Asia, but human infections so far remain rare.
Experts agree it is only a matter of time before a deadly human flu pandemic flu develops, and most suspect that the current bird flu strain is the most likely candidate, whether now or next time around.
"It's not a virus which we have been able to get rid of. It comes back, comes back and these outbreaks are getting bigger and bigger," Stohr said. "This is the virus which everyone would bet their money on."
There are two ways that the bird flu virus sweeping Asia could become a serious danger to humans.
In one scenario, it could accumulate enough genetic mutations on its own to become good at passing between humans. Experts are tracking the virus to detect any significant genetic changes, but so far none has been recorded.
The more scary option would be a sudden change in the virus, brought on by combining with a normal human flu strain in someone's body. The two viruses could swap genes and create a potent hybrid with the deadliness of the bird strain and the contagiousness of a regular human strain. It only takes one person with a double infection to set off such a chain of events, Stohr said.
Studies in monkeys will be conducted in the Netherlands and are expected to yield results by the end of next month.
They will test how the pure bird flu virus behaves in the body. Although a human pandemic would be a mix of this virus and a human one, it would still ravage in the same way. The mixing would make it more transmissible between humans, but the power of the original bird virus would remain.
The experiments are expected to answer many mysteries about how the virus might behave in humans, such as the incubation period, how long people will remain infectious, when antibodies will be detectable, when fever starts and subsides, how likely survival would be and whether the virus could be spread through urine or feces as well as saliva.
The tests will also help authorities determine whether it makes sense to close down schools and restrict travel.
One test that will be very important for determining how best to treat the virus will be autopsies on monkeys experimentally infected.
"We don't know whether this virus is spreading in the entire body or whether it's just in the lungs," Stohr said.
The two drugs that could be used to treat bird flu in people work differently in the body, he said.
"Tamiflu reaches therapeutic levels in many tissues. Relenza does not. It is only in the lung," Stohr said. "If this virus gets into the brain, the liver and other parts of the body, then Relenza would be out. We could only use Tamiflu."
"All these questions cannot be answered without doing the proper trials now," he said.
"We are getting ammunition. We don't want to go into battle without having a reconnaissance mission. We don't want to go into a pandemic without knowing what the enemy is, and that's what this is all about."
The laboratory studies, which are expected to start by the end of March, aim to understand how likely the bird flu virus is to mate with a normal human flu variety.
Some of the tests will involve placing the two strains together in bottles to see how easily they mix and to track which exact genetic reshuffles occur most frequently. Each virus has only eight genes, so the number of combinations will be manageable to study.
The tests will give clues to what kind of reshuffling is most likely to occur if a pandemic strain does emerge. If they face a pandemic based on the current bird flu, experts would then be able to distinguish between dangerous combinations and benign ones and respond accordingly.
The next step would be to inject the new hybrid into animals to see how it behaves. Ferrets would be used first, then perhaps monkeys.
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