We talk about bacteria and viruses making us ill, you might also hear them referred to as pathogens. Pathogen is a general term for any microorganism which can cause disease. This post looks at how bacteria are different to viruses and includes a virus and bacteria comparison table.

What is a pathogen?

Bacteria, viruses, protists and fungi can all be pathogens.

Bacteria image
Bacteria under a microscope

Differences between bacteria and viruses


Bacteria are bigger than viruses, but are still very small. They are about 1/100 the size of a normal body cell.

Bacteria are living cells.

Single cell organisms which can reproduce alone.

Not all bacteria cause disease, some are harmless and some helpful.

Some bacteria attack tissues of the body or release toxins which make you feel poorly.

Antibiotics can be used to destroy bacteria.


Viruses are smaller than bacteria. They are about 1/100 the size of a bacterium.

Viruses are not a living cell, they are a strand of genetic information ( DNA or RNA ) inside a protein coat. They can only reproduce inside a living cell.

Viruses invade cells where they use the cells machinery to make many copies of themselves. The new viruses are released from the host cell to search for a new cell to take over.

Antibiotics do not affect viruses. Some viral diseases are treated with antiviral medication.

How are bacteria different to viruses

Bacteria are bigger than viruses and are classed as a living organism which can reproduce without a host cell.

The question of whether viruses are a living thing is not straightforward.

Examples of diseases caused by bacteria

Cholera ( Vibrio cholerae ) is spread by bacteria in drinking water. Usually from faeces of an infected person contaminating drinking water.

Tuberculosis is caused by Mycobacterium tuberculosis and mostly affects the lungs although it can impact other organs as well.

Examples of diseases caused by viruses

One of the most common viruses you hear about is Influenza. This is an airborne virus. When an infected people coughs or sneeze the virus is expelled into the air in droplets which can be breathed in by people close by.

Chicken Pox ( Varicella Zoster ) is a childhood virus that is transmitted in the air from an infected person coughing or sneezing. Chicken Pox can also be spread by direct contact with chicken pox blisters or the mucus or saliva of an infected person.

What is a communicable disease?

A communicable disease is one that can easily spread. Diseases can spread between people, between animals and people or even between plants.

Pathogens can spread in water, in the air or by touching a surface contaminated with an infectious agent.

Plants and animals can be infected by pathogens.

Bacteria and Virus Activities for Kids

Make models of viruses using play dough or plasticine.

Make a snot trap and find out why snot is so fantastic!!

Not all bacteria are bad

Some types of bacteria do cause nasty diseases, but our bodies are also home to trillions of good bacteria. They help us digest food, produce vitamins and it’s also thought good bacteria help protect us from bacteria that cause illnesses by overcrowding them!

Some people take a food supplement called a probiotic to increase the amount of healthy bacteria in their body.

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Image of bacteria and viruses to show the difference between the two

The post How are bacteria different to viruses? appeared first on Science Experiments for Kids.

Originally posted at Science Sparks