Difference Between Viruses & Bacteria: Lesson for Kids

Instructor: Rachel Torrens
Bacteria and viruses are both germs, but what makes one different from the other? In this lesson, learn the differences in size, structure, and reproduction of bacteria and viruses.

What is a Germ?

Barbie and Vick are sick. Barbie has a fever and sore throat. Vick has a fever and little red spots all over his body. What is causing the illnesses in these children? Well, germs!

When we talk about 'germs', we are usually talking about something that can make someone sick. In the case of Barbie and Vick, it is actually different types of germs that are making each of them sick.

Barbie is sick because of bacteria, specifically strep throat. Vick is sick, but from a virus called chickenpox. Bacteria and viruses both make you sick; however, what are the differences between the two?

Before moving on, it's important you understand that a single bacteria is called a bacterium. If there is more than one bacterium, the correct term is bacteria. Like if you see one furry critter it's a mouse; but if you see two, it's mice. Now that you've got that down, it's time to explore what makes these germs different!

Let's Look at the Differences

Bacteria and viruses are more different than alike. The major things that separate the two are:

  • Size
  • Structure
  • Reproduction


Bacteria are really big in comparison to viruses. An average bacterium is 1,000 nanometers long. On the other hand, the largest virus is only 250 nanometers long, and most viruses tend to be much smaller.

The average bacterium is much larger than the largest virus!
Diagram of bacterium and virus size

So if you imagine a bacterium is the size of a school bus, then the largest virus would be the size of a motorcycle. And most viruses would be the size of a skateboard. Think bacterium, think big!


As for structure, bacteria are extremely complex, whereas viruses are very simple. A bacterium has a cell wall around the outside. Inside, the bacterium is filled with all sorts of important structures necessary for life, including a genetic code. Genetic codes are the building blocks from which all living things are made, either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid).

A bacterium has a complex structure, including a cell wall, proteins, ribosomes, mitrochondria and DNA!
Bacterium structure

On the other hand, a virus is an outer envelope filled with genetic code. That's it! There are no additional structures on the inside.

A virus is built very simply of an outer protein envelope that is filled with genetic code, either DNA or RNA.
Virus structure

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