ENDEMIC. An adjective signifying that a given infectious disease is constantly present in a population in the sense that a few cases may always be detected on careful search. An endemic disease is liable to assume epidemic proportions (see EPIDEMIC) under conditions that are not fully understood. No doubt in endemic diseases, as in the occurrence of epidemics, the existence of chronic carriers of the disease amongst the population (see CARRIERS) is of fundamental importance, but the factors of sus ceptibility and immunity amongst the healthy (see IMMUNITY) are equally important and far more difficult to determine. (See