EPIDEMIC ( La . ilk. iTio/mor, among the people. from . pi, 111)1131 (Pm 08, p1.01111. A name applied to diseases h ieh app.. ral :Ind spread over a VI•rt a in orea, or Iraven, a large section of the world, and attack si la riv. number of people. An modemie disease may become endemic (q.v.), and remain permanently in a locality. Cholera is epidemic in certain parts of Europe, at inter vals subsiding and disappearing; while it re mains endemic in India. Probably all diseases which are epidemic in various parts of the world are endemic in certain localities, and the epi demics are brought by travelers from these localities; or follow commerce under favoring conditions, such as starvation during famine, debility dependent upon exposure to miasmata after inundations; swarming and migration of insects which carry contagion, etc. Drainage and paving of streets result in checking and eradicating an epidemic of malaria in a town. Opening the pavements and tunneling the streets afford harbors in damp spots and puddles for mosquitoes, which propagate rapidly, become infected with the plasmodium of malaria, and transmit the micro-organism to human beings; and thus an epidemic of malaria is started. Epi demics of typhoid fever are almost invariably traced to one or a few cases of the disease, from whose excrement drinking-water has became pol luted. Epidemics are due, primarily, to dis
semination of bacterial germs, though in some diseases of the contagious class (such as scarlet fever and smallpox) the causative germs have not yet been isolated. They must be checked, therefore, by bacteriological precautions. It is difficult to explain the cause of certain cycles in which epidemics appear to move, regularly recur ring in certain localites: hut in all cases pre cautions should be taken to quarantine people entering a pdrt from an infected country, and clothing and all merchandise should be disin fected. Serum therapy (q.v.) promises a pro tection against many epidemic diseases, as well as treatment during disease.
Epidemics of nervous diseases have appeared at times in the history of the world: as of chorea (q.v.), or of dancing mania. Under the leadership of a person afflicted with paranoia (q.v.), many people of unstable mental equilib rium have been dominated by suggestion (q.v.), and the results hare been crusades, persecution of 'witches,' epidemics of suicides, etc. Con sult. Hecker, Epidemics of the Middle Ages, trans. by Babington (London, 1849). See CLIMATE; CONTAGION; INFECTION; CHOLERA; TYPHOID FE VER, etc.