Virus a mysterious story

You must be thinking, why I have taken viruses as “mysterious story”?. Medical science has many stories of success, but when it comes to viruses why it gets failed? Answer is hidden in their extraordinary behavior and life-cycle they exhibit. Viruses are so complex that it is even difficult to say, whether they are living or non-living. Many of the viral diseases are not permanently curable and the reason is again behind the mysterious story of their behavior.
Pasteur gave the name viruses that means venom or poisonous fluid. I am sure, we all have suffered from the ‘common cold‘. Even by this ‘common cold’ we can associate how much ill effects any viruses can cause. Viruses are not even assigned to any classification group as they are not true ‘living’. Viruses, basically do not have a cellular structure. Viruses are inert and have crystalline structure, consisting largely of proteins. This is all they show when they are outside the host cell. But when they enter a living cell there comes a mysterious story of viruses. Non-living behavior gets transformed. They take over the machinery of the host cell to replicate themselves leading to the killing of the host cell.
If you are comparing the size of human cell with any virus, virus have too much small structure. They even pass through the bacteria-proof filters.  A virus is basically a nucleoprotein, in which genetic material is deadly for the host. Genetic material could be either DNA or RNA, both are never present in same virus. Virus that infect plants are mostly single stranded RNA and which infects animals could be single or double stranded RNA or double stranded DNA. Their crystalline structure largely consists of proteins. The protein coat protects the genetic material. Capsomeres are the small subunits of protein coat. Those viruses which do not contain this protein coat are called viroids, they just have free genetic material.
Virus functioning is based on the host genome. They incorporate their genetic material into the host genome. The infected host cell is now directed to produce new viral copies. New viruses produced in turn infect other healthy cells of the host. This is basic mechanism, how any virus causes infection in the host cell.
Virus cause number of diseases such as smallpox, common cold, chickenpox, influenza, polio, rabies, AIDS, Ebola. Even some types of cancer are linked to viruses. Antibiotics are useless against many of the diseases and antiviral drugs are effective against for few viral diseases only. It is very difficult to kill any virus. This is the reason “story of viruses is mysterious” and there is no proper treatment for many of the viral diseases to the medical science.