兄弟姐妹们，谁能给我一篇关于病毒的英文文章 谢谢啊

A virus (from the Latin virus meaning toxin or poison) is a sub-microscopic infectious agent that is unable to grow or reproduce outside a host cell. Viruses infect all cellular life. The first known virus, tobacco mosaic virus, was discovered by Martinus Beijerinck in 1899,[1] and now more than 5,000 types of virus have been described.[2] The study of viruses is known as virology, and is a branch of microbiology.

Viruses consist of two or three parts: all viruses have genes made from either DNA or RNA, long molecules that carry genetic information; all have a protein coat that protects these genes; and some have an envelope of fat that surrounds them when they are outside a cell. Viruses vary in shape from simple helical and icosahedral shapes, to more complex structures. They are about 100 times smaller than bacteria.[3] The origins of viruses are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—while others may have evolved from ba