What Is a Virus and What Is a Bacterium? What’s the difference?

We know that we can be subject to a viral infection or a bacterial infection and also that the methods of treating either are quite different. For instance antibiotics are no good for treating a viral infection.


However it is difficult for the lay person to understand what exactly the difference between virus and bacteria is. Let us try to understand what the difference between virus and bacteria is, so that we can better understand why both kinds of infection have to be treated differently.

Both bacteria and viruses can cause infection yet the type of infection and they way they run their course and the way they are treated is different.


Firstly a virus is an infectious agent, whereas a bacterium is a living organism.

There is some dispute in the scientific community as to whether virus can be considered to be a living organism or whether it is to be classified, but in general viruses are not considered living in the same way as bacteria.


Bacteria are unicellular (single cell) creatures whereas viruses are non-cell creatures. Bacteria are not visible to the naked eye, but viruses are even smaller and are not even visible with the help of a regular microscope. The average virus is one-hundredth the size of the average bacterium.


While bacteria can multiply or reproduce on their own viruses cannot. Viruses are parasites that cannot function without a host organism to feed on. They can multiply only by infecting a host organism, then taking over the cells of the host and then causing those cells to create copies of itself. In the process the host cells are also destroyed.

Type of infection

The type of infection caused by a bacterium is localized whereas that which is caused by virus is systemic. The treatment that is used for a bacterial infection is antibiotics, which helps to kill inimical bacteria. Viral infections on the other hand are prevented by the help of vaccines. If a viral infection does occur, the reproduction of the viruses can be slowed down but not prevented by anti-viral medications.

Beneficial or inimical

Another major difference is that there are many kinds of bacteria that are friendly to us, and which are beneficial in the normal functioning of the body. No virus on the other hand is beneficial, though of late their uses in genetic engineering and destroying cancer are being explored.