http://ca.news.yahoo.com/s/23052006...ird-flu-cluster-human-human-human-spread.html WHO, May.23 (CP): The large cluster of human cases of H5N1 avian flu being investigated in Indonesia may represent the first time the virus has been seen to ignite two successive waves of human-to-human spread, the World Health Organization said Tuesday. A spokesperson said the agency has not yet started the process of reviewing whether the global pandemic alert level should be raised to Phase 4 from the current Phase 3. But Maria Cheng said it is conceivable that WHO might convene a meeting of the panel of experts who would advise on that decision - depending on what further investigation in the affected area reveals. "This is the first time we have seen cases that have gone beyond one generation of human-to-human spread," Cheng told The Canadian Press. "It is an evolving situation and it is possible we would convene the task force if we saw evidence the virus was changing." According to the WHO's six-level pandemic staging plan, Phase 3 is no human-to-human spread, or only on rare occasions after close contact with a sick individual. Phase 4 is a small cluster or clusters of limited and localized human-to-human spread, a pattern suggesting the virus had not yet become fully efficient at infecting people. Phase 6 is a pandemic. Cheng noted the pattern of infections in this cluster seems to point away from a substantial change in the transmissibility of the virus. So do the genetic sequences of two viruses retrieved from this group of people. A statement from the WHO said analysis of those viruses showed "no evidence of significant mutations." But a veteran U.S. infectious diseases expert said he's worried the world may be seeing something different with this group of cases. "Certainly there've been more cases in this cluster than we've had before," said Dr. D.A. Henderson, of the Center for Biosecurity of University of Pittsburgh Medical Center. Previous cases of human-to-human transmission of the H5N1 virus are believed to have happened, but it is thought that in those earlier instances the virus died out after one generation of person-to-person spread.