Can you remember an instance when you suffered from fever, cough or a cold? It is difficult to find a person who has not suffered one of these. In the same way you may have wondered from whom you contracted the disease. Most probably you may have been infected with a communicable disease. This is a disease that is transmitted by a germ which can be a bacteria or a virus. There are also diseases which not transmitted by vectors. Very often you will have to face the challenge of avoiding various diseases. Therefore you should be aware of such diseases.