(a) : Mumps is an infectious disease causing fever, difficulty in opening the mouth and painful swelling of the parotid glands which lie just below the lobe of the ears. It is caused by a Paramyxovirus, which comes out in the saliva of the infected person. Rabies (Hydrophobia) is caused by a virus named as rabies virus. It is introduced in the body by the bite of rabid (mad) dogs usually. Fear of water is the most important characteristic symptom of this disease. Other symptoms are saliva from the mouth, severe headache, high fever, alternating periods, of excitement and depression, inability to swallow even fluids due to choked throat. The virus destroys the brain and spinal cord. Rabies is 100% fatal. Cholera and tuberculosis are bacterial diseases caused by Vibrio cholerae and Mycobacterium tuberculosis respectively. Typhoid and tetanus are bacterial diseases caused by Salmonella typhi and Clostridium tetani respectively. AIDS is caused by HIV (human immunodeficiency virus). Syphillis is caused by spirochaete Treponema pallidum.