An estimated three to six shifts occurred in the 18th century, four in the 19th, and three in the 20th: the 1918 pandemic, the 1957 Asian flu and the 1968 Hong Kong flu.

• 据估计，十八世纪发生了三至六次的大变异，十九世纪四次，二十世纪三次，分别是一九一八年的流感大流行、一九五七年的亚洲流感和一九六八年的香港流感。