这季节性的流感多发于65岁以上老年人有着明显的不同。

This is in contrast to the tendency of seasonal flu to affect mostly elderly people over the age of 65 years.

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相反的，季节性的流感多发生在瘦弱的老年人身上。

In contrast, seasonal flu tends to kill the frail elderly.

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H7N9禽流感病毒可能大多发生在冬季和春季，中国首次报道人类感染禽流感是在2013年三月份。

H7N9, a bird flu strain most likely to strike in winter and spring, was first reported to have infected humans in China in March 2013.

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