the germs that make people sick are everywhere. You can't see them, but they're there. they're sitting on your desk. they're hiding on your computer's keyboard. they're even in the air that you are breathing. there are two types of germs: viruses and bacteria. Viruses are germs that can only live inside animals or plants. Viruses cause illnesses such as the flu and measles. Bacteria are tiny creatures. Some bacteria are good. They can help your stomach break down food. Other bacteria aren't so good. they can make you sick. Bacteria can cause sore throats and ear infections.