A thief with many master keys

When I looking up to the sky, a bird has flown away to the East so quickly in spite of the effort to flap were vain, probably relatively strong wind is blowing there, it a typical winter weather today. It will return to it's nest after a wind settlement.

Whatever it is alive, there is a certain way of living there, but when it comes to viruses, the story is completely different. They do not have the vital activity of ingestion, metabolism and excretion, and in that sense they are not living things. It means that Virus can continue it's property unlimitedly without any metabolic performance. Continuing without food is the strongest property at all, they are far above to us.

When they reach a living cell and the breeding conditions are met, they break the cell membrane, and when they reach the nuclear envelope, they secrete a specific enzyme that breaks the well-protected protective barrier and enter the nucleus. Once they allow entry, the cell is hijacked. Many copies of the virus are produced in it, and when it is full, it bursts and is released to the outside at once. This condition is called virus infection. 

When a virus makes its own copy, it is not always done exactly exactly, and a failure occurs. In other words, a different one is made. This is called a mutation and naturally has different infectivity and toxicity. An event that always occurs in a host. That is, different things can always be made. In other words, the characteristics of the invading virus and the excreted virus can be considered to be different. Some kind of mutation has been performed.

There are many types of receptors in the nuclear envelope, and it is skillful. Only the virus that can bind to the receptor can enter. That is why it is likened to a thief with many master keys that fit the keyhole.