原文如下:
The World Health Organization said Thursday that up to 2 billion people could be infected by swine flu if the current outbreak turns into a pandemic. The agency said a pandemic typically lasts two years.
WHO flu chief Keiji Fukuda said the number wasn't a prediction, but that experience with flu pandemics showed one-third of the world's population gets infected.
"If we do move into a pandemic then our expectation is that we will see a large number of people infected worldwide," Fukuda said. "If you look at past pandemics, it would be a reasonable estimate to say perhaps a third of the world's population would get infected with this virus."
