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Updated on March 5, 2013

Viruses are minute organisms with the ability to cause infections in all cellular life forms. Viruses are unique in their formation because they are only made up of proteins and having the genetic material either DNA or RNA. The genetic material is comprised of information needed for the virus to make more viral copies or particles. The viruses can cause illnesses when they enter inside the cell with the aim of replication and survival because viruses are non living entities outside the living host. They are on the border line between the livings and non- living therefore for their survival and replication viruses need living host which results in a type of infections. The viral infected cell expires because they loss control over their machinery and cell division which give rise to the cancerous condition in the body while sometimes the cell is infected by virus but is present in the dormant state in the cell so that didn’t cause any infection or disease.

Viruses cause infections first by attachment to the specific receptors present on the host cell surface, the attachment may be reversible or non reversible. In reversible attachment only viral genome is inserted into the host cell through the formation of pore on the cell surface of host while on the other hand in non reversible attachment the entire virus enters the cell by carrying out the process of endocytosis that may be either clathrin- mediated endocytosis or cavolin-mediated endocytosis produces the endosome that is a vesicle containing the virus, the endosome then fuses with lysosome which lowers the pH of the endosome, results in the lysis and releases of virus particles inside the cell, in this way virus enter the cell and using host cell replicating machinery the virus make number of copies of their genome and give rise to the successive infection in the host cell. When the cell depart its life the newly synthesized viruses came out of this cell and are free to infect new cell and in such manner they initiates the infection and disastrous disease when they take control over the machinery of the host cell like hijackers.

Viruses can cause two types of infection non-productive infections and productive infections. In productive infection the progeny virons are synthesized in that cell which is first infected by virus then these progeny is released upon lysis of that cell and spread to infect other healthy cells of the body like this they cause the successful or productive infection while in non-productive infection the virons are not able to initiate a disease but can do it only under certain specific set of conditions.

The non- productive infections are further divided into latent infections. The infection is initiated when the viral genome is retained in the host cell genome or may be present in the form of covalently closed circular DNA in such conditions the virus is in dormant state and cannot perform any function so in this case they are not able to cause disease. The latent infections can be reverted back to the productive one when the conducive conditions are provided to the cell like the cell became immunocompromised, irradiation of cell with UV light, the phase of the cell cycle or the coinfection of the cell with the satellite or helper virus.

Abortive infections the type of non productive infection is not like latent the viral genome does not persist in host cell but became abortive due to cellular environment and can initiate the booming infection in permissive cells that may kill the host. The virons involved in such type of infections is known as defective viruses.


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    • profile image

      Farhan Ahmad 

      5 years ago

      it is a nice artical about the viruses and about their entry and types. overall a good narrated and well managed one with quite an information gathered into in.

      keep it up....

      waiting for the next....


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