New virus less than pandemic

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http://www.usatoday.com/tech/science/genetics/2006-07-31-new-flu-virus_x.htm?POE=TECISVA New virus less than pandemicPosted 7/31/2006 6:54 PM ET By Anita Manning, USA TODAY Using a new method to test potential pandemic flu strains, scientists have created a virus that contains genes from human and bird flus and found it lacks what it takes to cause a pandemic. The researchers combined genes from a human flu strain, H3N2, and the H5N1 bird flu strain that emerged in Hong Kong in 1997, which is an earlier version of the deadly strain that is circulating in parts of Asia, Africa and Europe. They found that in animal experiments, the mixed virus lacks "the key property that predicts pandemic spread." But experts say other gene combinations or mutations could turn H5N1 into a

pandemic strain. "We are far from out of the woods in H5N1 on a global scale," Gerberding, director of the Centers for Disease Control and Prevention, said in a briefing on the study, which was published Monday in the Proceedings of the National Academy of Sciences. "These data do not mean that H5N1 cannot convert to be transmissible from one person to another person," she said. "They mean that it's probably not a simple process and more than simple genetic exchanges are necessary." In four experiments, CDC scientists used reverse genetics to create a virus with both bird flu and human flu genes. They gave the hybrid strain to ferrets, which are good models for human flu studies because they have similar respiratory tract cells. They found the virus containing genes from both bird and human flu strains was weaker than

either parent virus. It caused milder illness and didn't spread easily. The experiments were risky in that "the possibility was there" that a highly transmissible pandemic strain might have been created in the lab, said researcher Katz, "but the study was conducted using the most stringent safety precautions" in a biosafety level 3 lab. Researchers used the combination they thought would have the greatest likelihood for transmission, but there are more than 50 other combinations possible. "Our results can't be generalized, and they're only relevant for the viruses we used in the study," which were the 1997 strains, Katz said. The researchers "didn't test the more recent strains (of H5N1) for their ability to transmit. We need to continue these studies." The study is "really important from the perspective of developing a useful lab tool that we can use to

study these viruses and combinations of genes," said Duchin of the Infectious Diseases Society of America and chief of communicable disease control at Public Health Seattle and King County, Wash. But "it doesn't tell us anything about the likelihood of this virus becoming a pandemic in the near future. We need to go on preparing with a sense of urgency and being sure we keep pandemic preparation as a priority." __________________________________________________