unit10中英对照翻译.docVIP

Viruses and viral diseases Viruses are the smallest of the pathogens, being approximately 1/500th the size of bacteria. Because of their small size, they are visible only under an electron microscope and were identified in humans only in the 1930s. Not until the1960s were viruses effectively grown outside of the body in tissue cultures. 病毒和病毒性疾病 病毒是最小的病原体，大小只有细菌的1 /500。由于其体积小，它们只在电子显微镜下可见和在1930年代的被人们鉴定出来。直到20世纪60年代，人们才得以在人体之外用组织培养的方式使病毒生长。 At the present time over 150 viruses are known to cause diseases in humans. The role of viruses in the development of various cancers and chronic disease is still unclear. In fact, viruses themselves are perhaps the most unusual of the microorganisms that infect humans. 目前有150以上种病毒是已知的能导致人类疾病的。病毒在各种癌症和慢性疾病的发展中的作用仍不清楚。事实上，病毒本身也许是最不寻常的能感染人类的微生物。 Essentially, a virus consists of a protein structure that contains the nucleic acids ribonucleic acid (RNA) or deoxyribonucleic acid (DNA). They have no capacity for carrying the normal cell functions of respiration and metabolism. Some scientists even question whether or not viruses should be considered living organisms. Viruses cannot reproduce on their own; rather, they must exist in a parasitic relationship with the cells they invade. 基本上，一个病毒是由一个蛋白质结构包含核酸的核糖核酸（RNA）或脱氧核糖核酸（DNA）构成。它们没有携带呼吸和代谢的正常细胞功能的能力。一些科学家甚至质疑病毒是不是应该归类为生物。病毒自身不能繁殖；确切来说，它必须与被其入侵的细胞形成寄生的关系而存在。 Once viruses attach themselves to host cells, they inject their own RNA and DNA,causing the host cells to begin reproducing new viruses. Once they take control of the cell, these new viruses overrun it until it fills to capacity and bursts, putting thousands of new viruses into circulation to begin the process all over again. This whole reproduction process may take as little as 20 seconds! 一旦病毒附着到宿主细胞，它们会注入自己的RNA和DNA，造成宿主细胞开始复制新的病毒。一旦它们控制了细胞，这些新的病毒会大量蔓延，直至整个细胞无法包容而破裂，成千上万的新病毒进入循环，开始新一轮的扩张。这整个复制过程可能只需花20秒！ Because viruses cannot reproduce outside of living cells, they are particularly difficult to culture in a laboratory, makin