What is a Virus?
A virus is a tiny submicroscopic viral agent that infects only inside an organism’s living cells. Viruses can infect all living things, from plants and animals to humans, including archausts, bacteria and fungus. They cause the same type of diseases as their hosts, and can invade tissues by means of a cut or break in the outer protective membrane.
The major types of viral diseases are herpes, cold sores, HIV/AIDS, cytomegalovirus, poliovirus, herpes simplex virus, Epstein-Barr virus ( Epstein-Garray) and viral meningitis. All these viruses are enveloped viruses – i.e. particles of viral DNA that lie between the viral envelope and the protein coating of the host cell. When a virus enters a living cell, it uses the host’s cellular machinery to replicate itself. This replication process uses the genes of the virus that enters the cell. If there is any error in the replication process, the viral genes can be copied and become part of the host cell instead.
Every viral disease has different symptoms. For example, people with cold sores are not likely to develop pink fever. The virus that causes genital warts may give sufferers pain and discomfort, but they will not have fever. These differences make it difficult to diagnose the condition correctly, and can make it difficult to treat successfully.
Viruses are a kind of “genetic hitchhikers”. They insert themselves into other organisms without causing any modifications in the host’s genome. The insertion of viral genes makes the new organisms much easier to manipulate than it would be if their genome was different from those of its parents. The viral genes involved, in this case, are the genetic material contained in the genes of the target organisms. The insertion of these genes disrupts the target organism’s normal genetic code, and thus allows the invading virus to reproduce itself.
There are two main categories of viruses: living and nonliving. Living viruses are able to duplicate themselves and infect living organisms. Nonliving viruses cannot reproduce themselves but can only infect nonliving things. Although viruses that are not living do not usually cause any harm to humans or other living things, they can still cause problems when they infect other nonliving things, sometimes causing disease.
Most viruses are spread by contact with the viral particles within the host cell. In order to spread a virus, the virus must latch on to an area of the target cell that is already populated by cells from another source. This makes it difficult to pass along the viral particles through bodily fluids or air, making the majority of viruses highly contagious.