Early in 1942 American military forces began their countermove to stem the rapid Japanese advance in the Pacific. The accomplishment of this task required the military occupation of numerous widely separated tropical islands throughout a vast subequatorial region and involved the establishment of bases on islands known to be hyperendemic foci of disease. There followed, as a consequence, a series of outbreaks of tropical diseases in epidemic proportions of a magnitude and potential threat seldom if ever exceeded in American military history.
Many factors contrived to create a situation which would favor a wide-scale outbreak of disease in the very early phases of the Pacific campaign. The initial occupation, of necessity, took place with a haste which did not permit carefully considered plans of disease prevention. The newly occupied islands were known to be endemic centers of an impressive array of threatening diseases, such as malaria, dengue, dysentery, scrub typhus,