What are infectious diseases? Is that caused by viruses?
Infectious diseases are those that are caused by an infecting agent or organism. They may be caused either by viruses, like chicken-pox, measles or mumps, or by bacteria, like tuberculosis or cholera, by protozoa, like malaria, or less commonly by fungi, like thrush, or prions, like Jakob-Creuzfeldt disease. The transmission is not necessarily directly from person to person. It may be via an animal (mosquito bite), or the environment (MRSA, the various diarrhoeal disorders).
