GENEVA – Up to 2 billion people could be infected by swine flu if the current outbreak turns into a pandemic lasting two years, the World Health Organization said yesterday. WHO flu chief Keiji Fukuda said the historical record of flu pandemics indicates one-third of the world's population gets infected in such outbreaks. Independent experts agreed that the estimate was possible but pointed out that many would not show any symptoms.
In Mexico, the hardest hit country so far, high schools and universities opened for the first time in two weeks as the government's top health official insisted the epidemic is on the decline. All students were checked for swine flu symptoms and some were sent home.
"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."
With the current total population of more than 6 billion, that would mean an infection total of 2 billion, he said, but added that the world has changed since pandemics of earlier generations, and experts are unable to predict if the impact will be greater or smaller.
"We don't really know." said Fukuda. "This is a benchmark from the past. Please do not interpret this as a prediction for the future."
So far the swine flu virus has spread to 26 countries. Brazil and Argentina on Thursday became the second and third countries in South America to announce confirmed cases.
U.S. health officials are no longer recommending that schools close because of suspected swine flu cases since the virus has turned out to be milder than initially feared. But many U.S. schools have done so anyway, including the school of a Texas teacher who died.
Experience is spurring the WHO to make sure the world is as prepared as possible for a pandemic, which would be indicated by a rise to phase 6 from the current phase 5 in the agency's alert scale. That would mean general spread of the disease in another region beyond North America, where the outbreak so far has been heaviest.
"I'm not quite sure we know if we're going to phase six or not or when we would do so," Fukuda said. "It's really impossible for anybody to predict right now."