A virus came from the Latin virus meaning "toxin" or "poison". It is sub-microscopic infectious agent that unable to grow or reproduce outside a host cell. Each viral particle which are also called virion consists of genetic material, DNA or RNA, within a protective protein coat called a capsid. The shape varies from simple helical and icosahedral forms, to more complex structures with tails or an envelope. Viruses infect all cellular life forms and grouped into animal, plant and bacterial types, according to the type of the host infected.
Examples of diseases caused by viruses include the common cold, influenza, chickenpox, diarrhea and cold sores. Serious diseases such as Ebola, AIDS, avian influenza and SARS are caused by viruses. The ability of viruses to cause disease is described in terms of virulence. Viruses have different mechanisms which they produce disease in an organism, which largely depends on the species. Mechanisms at the cellular level primarily include cell lysis, the breaking open and subsequent death of the cell. In multicellular organisms, if enough cells die the whole organism will start to suffer the effects. Although viruses cause disruption of healthy homeostasis, resulting in disease, they may exist relatively harmlessly within an organism.
Some viruses can cause chronic infections, where the viruses continue to replicate in the body of the hosts' defense mechanisms. Biologists debate whether or not viruses are living organisms. Some consider them non-living as they do not meet all the criteria used in the common definitions of life. For example, unlike most organisms, viruses do not have cells. However, viruses have genes and evolve by natural selection. Others have described them as organisms at the edge of life. Viral infections in human and 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 that produce lifelong immunity can prevent viral infections.
Examples of diseases caused by viruses include the common cold, influenza, chickenpox, diarrhea and cold sores. Serious diseases such as Ebola, AIDS, avian influenza and SARS are caused by viruses. The ability of viruses to cause disease is described in terms of virulence. Viruses have different mechanisms which they produce disease in an organism, which largely depends on the species. Mechanisms at the cellular level primarily include cell lysis, the breaking open and subsequent death of the cell. In multicellular organisms, if enough cells die the whole organism will start to suffer the effects. Although viruses cause disruption of healthy homeostasis, resulting in disease, they may exist relatively harmlessly within an organism.
Some viruses can cause chronic infections, where the viruses continue to replicate in the body of the hosts' defense mechanisms. Biologists debate whether or not viruses are living organisms. Some consider them non-living as they do not meet all the criteria used in the common definitions of life. For example, unlike most organisms, viruses do not have cells. However, viruses have genes and evolve by natural selection. Others have described them as organisms at the edge of life. Viral infections in human and 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 that produce lifelong immunity can prevent viral infections.
2 comments:
Based on my knowledge, virus is an acellular organism which can cause serious illness. Is virus alive?
Because it can reproduce just like human eventhough viruses do not respire and move.
Added information for us;
the current virus that always infect human beings is Adenoviridae which can cause conjunctivitis, tonsillitis (strep throat), gastroenteritis and lead to death.
Beware!
~Microbiology rules~
(^_^)
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