There are three types of seasonal influenza – A, B and C. Type A influenza viruses are further typed into subtypes according to different kinds and combinations of virus surface proteins.

有三种类型的季节性流感——甲型、乙型和丙型。 根据病毒表面蛋白不同的种类和结合情况，甲型流感病毒又进一步分类为亚型。

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It is a contagious respiratory disease of pigs caused by type a influenza viruses. Pigs are hit by regular outbreaks.

猪流感是由A型流感病毒引起的猪呼吸道传染病，病毒的定期爆发会引起猪患病。

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Shell viruses wrap themselves around a host program and don't modify the original program．Shell programs are easy to write，which is why about half of viruses are of this type．

外壳型病毒将它们自己包裹在主程序的四周，对源程序不作修改。 外壳型病毒容易编写，这也正是约有一半病毒程序是这种类型的原因。

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Different sorts of viruses have different weights, but all viruses of a particular type weigh the same amount.

ECONOMIST: Small-scale physics

The H5 in H5N1 stands for hemagglutinin type 5, meaning the fifth known type of hemagglutinin found on the coatings of influenza viruses.

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Meanwhile, Jillian Shapiro of Mount Sinai Medical School figured out away to get another new type of genetic material, called microRNA, into cells using viruses.

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