"The Norwegian Institute of Public Health has informed WHO of a mutation detected in three H1N1 viruses," the WHO said in a briefing note....the agency revealed that a similar mutation had been observed in Brazil, China, Japan, Mexico, Ukraine, and the United States, as early as April.
Scientists fear that mutations in flu viruses could cause more virulent and deadly pandemic flu. The global health watchdog reiterated a call for close monitoring.
The WHO was still assessing the significance of the latest observation, but it stressed that many such changes in the flu virus do not alter the illness it causes in patients."
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