Genes of new flu virus show it's not so new

WASHINGTON (Reuters) - The most complete analysis yet of the new H1N1 swine flu virus shows it must have been circulating undetected for years, most likely in pigs, researchers said on Friday. They said pigs are clearly a potential source of human pandemics. "The results of the study show the global need for more systematic surveillance of influenza viruses in pigs," Dr. Nancy Cox, chief of the influenza division at the U.S. Centers for Disease Control and Prevention, told reporters in a telephone briefing.