Health experts say its rapid transmission coincides with the southern hemisphere's traditional winter flu season.

卫生专家说，它的迅速传播正值南半球冬季传统的流感季节。

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During the regular winter flu season, elderly people and those with chronic health conditions are the most likely to be sent to a hospital.

在流感的常规流行季节冬季，老年人和那些患有慢性疾病的人被送往医院的最多。

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U.S.officials worry that, even if the virus' spread is eventually contained, it could re-emerge months from now during the northern hemisphere's winter flu season, when more than 30,000 Americans die each year from common influenza.

VOA: standard.2009.05.03

Mr Healey said it had been clear the current outbreak would not be like "normal winter flu because we knew swine flu would be dominant".

BBC: Government accused of 'misjudgement' over flu outbreak

On Monday, Thomas Lonngren, the head of the European Medicines Agency, said such a human vaccine might not be ready before next year's winter flu season.

ECONOMIST: The spreading bird-flu menace reaches Europe | The

The Hajj season -- dates vary depending on the sighting of the new moon -- peaks between Wednesday and Saturday this year, just as the winter flu season gets underway in the Northern hemisphere.

CNN: The Hajj: A perfect storm for swine flu?