Question

why some type of viruses could cause cancel while their is not any bacterial could cause cancer? what is the reason that make virus that virulence ?

Answer 1

Viruses are capable of causing cancer its so because Viruses are normally submicroscopic infectious agent that replicate only when inside the host body.Now whenever a virus infects the host it tends to release their genetic material into the host cells, whether its RNA or DNA depending upon the type of virus infecting.Now this released genetic material is incorporated into host cells genome and is replicated and leading to production of multiple copies of the virus which in turn infects the other host cells.For example The Human Papiloma Virus releases its DNA into the host DNA which inturn disrupts the normal function of cell and causes spread of the infection.

Thus due to the alteration in the host cell genome which in turn causes total disturbance in the host homeostasis leading to abnormal proliferation of cell and in turn leading to cancerous growth.Now in individuals infected with HIV there is a generalised immune deficiency that allows other oncogenic viruses to infect that individual and cause cancer.Some of the most common oncogenic viruses are Epstein Barr virus,Human Herpes Virus 8 etc.

Mainly there are 4 ways by which viruses cause cancer-

1 By directly damaging the DNA in host cells as mentioned in the first passage

2 Alteration of the immune system like in HIV infections

3 Causing severe chronic inflammation

4 Disruption of body homeostasis on cell division.

Thus certain viruses cause chronic inflammation of the infected part which in turn implies that there is increased rate of cellular proliferation thus giving rise to increased chance for origination of mutation.

Whereas bacterias do not cause cancer as there is no exchange of the genetic makeup between the bacteria and the host and moreover they are living microorganisms and thus pose less threat for cancer .Thus the viruses are more prone to cause cancer .

Viruses are so virulent because they have toxins ,surface coats that inhibit phagocytosis by immune system of the host cell.Moreover capacity to insert the virus DNA sequence into host cell makes it more virulent