One way of proving that a given disease is "infectious", is to satisfy Koch's postulates (first proposed by Robert Koch), which demands that the infectious agent be identified only in patients and not in healthy controls, and that patients who contract the agent also develop the disease. These postulates were first used in the discovery that Mycobacteria species cause tuberculosis. Koch's postulates can not be applied ethically for many human diseases because they require experimental infection of a healthy individual with a pathogen produced as a pure culture. Often, even clearly infectious diseases do not meet the infectious criteria. For example, Treponema pallidum, the causative spirochete of syphilis, cannot be cultured in vitro - however the organism can be cultured in rabbit testes. It is less clear that a pure culture comes from an animal source serving as host than it is when derived from microbes derived from plate culture. Epidemiology is another important tool used to study disease in a population. For infectious diseases it helps to determine if a disease outbreak is sporadic (occasional occurrence), endemic (regular cases often occurring in a region), epidemic (an unusually high number of cases in a region), or pandemic (a global epidemic). COUNT 5
QSN1 What is one way of proving that a given disease is infectious? ANS1 satisfy Koch's postulates QSN2 What must an infectious agent only be identified in to satisfy the first of Koch's postulates? ANS2 patients and not in healthy controls QSN3 What is Koch's second postulate? ANS3 patients who contract the agent also develop the disease QSN4 Why can't Koch's postulates be applied ethically for many human diseases? ANS4 because they require experimental infection of a healthy individual QSN5 What is the causative spirochete of syphilis?  ANS5 Treponema pallidum