Review paper Essay Example | Topics and Well Written Essays - 1000 words - 1

Review paper - Essay Example Their shape varies from simple helical and icosahedral (polyhedral or near-spherical) forms, to more complex structures with tails or an envelope. Viruses infect cellular forms of life and are grouped into animal, plant and bacterial viruses. There always been a discussion whether viruses are living organisms. Some consider them non-living as they do not meet the criteria of the definition of life. For example, unlike most organisms, viruses do not have cells. However, viruses have genes and evolve by natural selection. The viruses mutate and compete. They have been described as organisms at the edge of life. The main feature of virus is that it usually destroys or modifies the cell it infects , thus exist as a potential agent that could afflict mankind and cause numerous dieseases as ranging from common cold, rabies, small pox, mumps, polio ,chicken pox , measles, rubella, hemorrhagic fevers to the Acquired Immuno Deficiency syndrome. Viral infections in human as well as animal hosts usually result in an immune response and disease. Often, a virus is completely eliminated by the immune system. Antibiotics have no effect on viruses, but antiviral drugs have been developed to treat life-threatening infections. Vaccines th at produce lifelong immunity can prevent virus infections. The main area still now developed in antiviral therapy to stop the viral replication is targeted either on viral replication or the process of polyprotein clevage. Over a long period of known human history terrible epidemics involved humanity. The flu, smallpox, and plague killed millions of people. The epidemics of â€Å"Black Death† in the 14th century killed almost one third of Europe’s population. These terrible epidemics left traces in the genome of populations. There appeared a probability to resist diseases. Scientists find new surprising abilities of immunity to resist viral attacks. In this paper I would like to discuss some of the