When you are ill, you must be unhappy because your body becomes hot, and there are pains all over. You don’t want to work. You stay in bed, feeling terrible.
What makes you ill? It is germs. Germs are everywhere. They are very small and you can’t see them with your eyes, but you can find them with a microscope. They are very small and there could be hundreds of them on or in a very small thing.
Germs are always in dirty water. When you look at dirty water under a microscope, you will see them in it. So your parents will not let you drink dirty water.
Germs are found not only in dirty water, they are also found in air and dust. If you cut your finger, and if some of the dust goes into the finger, it will become big and red, and you will have much pain in it. Sometimes they will go into your body and you will have pain everywhere.