Your immune system is protecting you from germs and diseases all the time, without you even knowing it. A disease is a sickness that occurs when there is an upset or breakdown in the way your body usually functions. Most diseases make you feel sick or like something isn't quite right with your body, but some diseases upset places in your body that you can't really feel, like your blood, your bones, or your internal organs. Symptoms are the changes that you can see or feel when you have a disease. Coughing can be a symptom of having a cold.
People recover from some diseases in a short time.
Others last a long time. Some leave permanent damage. Other diseases can cause death. Our bodies have ways of protecting us. Our skin is strong and keeps out many germs and viruses.