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"In fact the evidence suggests that this is a naturally occurring virus, and not a laboratory-derived virus," Dr. Keiji Fukuda, WHO's acting assistant director-general for health security and environment, told a news briefing in Geneva.
Fukuda said the WHO made the conclusion after a series of discussions and valuations with scientists in its collaborating centers as well as from the UN Food and Agriculture Organization (FAO) and the World Organization for Animal Health (OIE).
The scientists took the hypothesis very seriously, but they concluded that "it does not really stand up to scrutiny," said Fukuda.
The Australian researcher, Adrian Gibbs, had suggested that the new flu virus may have accidentally evolved in eggs scientists used to grow viruses and drug makers used to make vaccines.