How do you feel when you hear the word germ?

Once, a long time ago, people didn’t know about germs so they weren’t scared of them. They didn’t know what made people sick. So they did things that spread the germs without knowing it.

Then 350 years ago a man called Antoni van Leeuwenhoek discovered germs. He was making microscopes that would let him see very small things. Being a scientist wasn’t his job – he actually sold fabric for people to make clothes. But he was very interested in finding out about the natural world. With his microscopes he could see things up to 200 times bigger than their real size. He saw tiny living moving things that he called animalcules. Now we call them germs. Your doctor would call these germs bacteria.

It wasn’t until 200 years later that scientists like Louis Pasteur and Joseph Lister worked out that these germs can cause disease.

Some germs called viruses are so small you can’t even see them with a microscope that makes things a thousand times bigger.

Now that we know about germs we know how we can protect ourselves from the germs that make us sick. A sick person can sometimes give their germs to someone else and make them sick. If germs are on your hands they can end up on whatever you touch. That’s why you should wash your hands before you eat or touch food.

But the good news is that our bodies have a system for attacking and destroying germs. This system is called the immune system. You might know that your blood has red and white blood cells in it. You also need a microscope to see these. The white blood cells in our blood are part of this immune system. They move around our bodies looking out for invading germs and attacking them. If you do manage to get enough germs to make you sick, your immune system fights them.

Here’s a video that explains how the immune system does this.

 

When you’re sick your immune system gets some good practice at killing the type of germ that’s making you sick. It also remembers that germ, so the next time it comes across the same type of germ it can get rid of it quickly and you don’t get sick.

A vaccine (shot) against a germ works by pretending to be that germ. It’s usually made of a harmless piece of the germ so it can’t make you sick. The immune system learns to recognise that bit of germ (it’s called an antigen). So when it meets the real live germ that has that antigen on it, your immune system knows it already. It can kill these germs really fast and you don’t get sick.

There are a lot of cleaning products that promise to get the germs out of our lives. Getting rid of germs must be good for us right? Well maybe not. We know that we should be careful with bad germs – the ones that can make us sick. But some germs are good for us. A lot of scientists now think that NOT getting enough different types of germs into our body is bad for us. They think our immune system needs to learn about lots of different germs, especially the ones that don’t hurt us, to learn how to work properly.

There are lots of different types of germs and they’re almost everywhere. The scientific name for germs is microbes. We actually have billions of them living in our bodies without making us sick. In fact they seem to be very important in keeping us healthy. They make up what’s called the microbiome. Right now scientists are learning more and more about the microbiome and how we can look after it.

 

Want to find out more?

There’s some good information about the cells and molecules of the immune system on the Biology for Kids website.

The Kids’ Health website has some more information about the immune system, a wordfind and a quiz (hint: watch the movie first).

More about Germ theory from Science Museum UK

More information about microbes that live in your gut – your microbiome from Learn.Genetics at Utah University

More about the microbiome and your health from HealthyChild.org

Some of the white blood cells (B-lymphocytes) make molecules called antibodies. These antibodies can lock onto a specific bit of the microbe (this bit is called an antigen – this is the part in a vaccine that makes it work) so the germ can be destroyed. There are millions of different B-lymphocytes and each one makes a different antigen. Once a B-lymphocyte finds the antigen that matches its antibody, it makes lots of copies of itself. All these copies of the B-lymphocyte make the same antibody that can fight that germ. Kidshealth.org has a lot more detail about this.