Swine flu spreads four times faster than other viruses and 40 per cent of the fatalities are young adults in good health, the world's top health official says.
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"This means that 40 per cent of the fatalities concern young adults - in good health - who die of a viral fever in five to seven days.

"This is the most worrying fact," she said, adding that "up to 30 per cent of people in densely populated countries risked getting infected."