How does the virus behave in human body?

Viruses are really small infectious factors. They consist of the core that has genetic information in form of DNA or RNA and the protein shell that is called capsid. Viruses cannot move or multiply themselves. To reproduce themselves they have to come into body cells that are alive. In the cell that was attacked, the virus multiplies itself, there are a lot new viruses and infected cell dies.

Various viruses attack various human cells for example HBV virus (causes hepatitis B) attacks livers cells, flu virus attacks respiratory tracts cells.

Virus HIV attacks blood cells that are responsible for the immunity (they are T4 lymphocytes). Genetic material of these cells is used by HIV virus to reproduce itself.

It makes the cell produce the copy of its fraction /segment as a result the healthy cell changes into the factory that produces copies of HIV virus and this process destroys the cell. After destroying some number of the cells the human body can not fight off any infections. The number of T4 lymphocytes is falling down with the evaluation of the infection. The falling down of the number lowers the ability to fight with infections because these cells are responsible for it. When the number of T4 cells falls down under 200/mm3, all the germs which normally would be destroyed by the immunity system, infect the human body. Developing in such a way infections are called opportunistic infections (opportunity is a quick possibility, occasion, convenient way) because they can develop when the human body is weak.

The essence of AIDS is the loss of the immunity which cannot fight with inquiring different germs into the body: bacteria, fungus, unicellular parasites or viruses and cannot fight with infections that are not dangerous when the people have immunity systems that are not destroyed. For people whose organisms are not able to combat as a result of HIV infection, the opportunistic infections have serious, usually fatal, process.