During seasonal epidemics, more than 90% of deaths occur in the frail elderly.

季节性流感期间，90%以上的死亡病例发生在体弱老人中。

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Many countries are reporting a mix of influenza viruses, again as is typically seen during seasonal epidemics.

许多国家报告出现流感病毒混合病例，又是通常发生在季节性流感流行期间。

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Why are we so worried about this pandemic possibility when thousands die every year from seasonal epidemics?

每年季节性流行病都会造成数以千计的人死亡，为什么我们会如此担心这一疾病大流行的可能性？

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But the new H1N1 flu has been affecting a younger age group than seasonal flu epidemics.

VOA: special.2009.08.05

But the H1N1 flu has been affecting a younger age group than seasonal flu epidemics.

VOA: special.2009.08.18

It is this continual process of genetic drift gives rise to the seasonal epidemics of flu and norovirus.

BBC: Winter bugs: A yearly battle for dominance