These words are used to describe diseases. Communicable and contagious are synonymous in designating that kind of disease which is conveyed by direct contact with an affected person or animal, or by contact with a secretion or discharge or by some article touched by him or it. Measles can be called either a communicable or a contagious disease. Communicable is a broader term than contagious in that it is also applied to diseases which are transmitted by some intermediary agent such as an insect. Malaria and yellow fever are examples of such communicable diseases. Infection refers to a disease which is caused by the invasion organism, especially bacteria and protozoa. Botulism and wound infections are infections diseases. Catching is an informal word used in place of all three of the other terms but more often as a substituted for communicable and contagious than for infections .