“It occasioned a great mortality—so much so, that the natives state, the living were not able to bury the dead.” James Jarves, Hawaii.1
Extraordinary infectious disease mortality depopulated many of the Pacific islands soon after they were first contacted by western explorers and sailors.2–4 The reasons behind the tremendous mortality remain largely unexplained, but apparently now no longer exist in the same island populations. Pacific islands were the last geographic points included in the global pathogen pool, and the admittedly fragmentary record of the earliest epidemics may offer insights into the mechanisms of mortality that presumably once existed for all human societies when they transitioned to live in interconnected populations.5,6 Most of the highly lethal Pacific epidemics preceded the scientific revolution created by Pasteur's discovery of the microbiological nature of infectious diseases, and were described by the few literate observers in archaic terms.3 Despite these limitations, the historical record offers the only definite information regarding potential explanations for the extraordinary mortality of first-contact epidemics.
Dysentery is a febrile infection leading to frequent defecation with blood, pus, and mucus in the stool. Shigella species are the most common cause of lethal (bacterial or bacillary) dysentery epidemics, and have been important factors in both historical and recent military campaigns and other complex public health emergencies.7–11 Although historical reports are often hard to fit into modern diagnostic categories, the descriptions of obvious blood in stool makes it highly likely that many of the early epidemics were indeed due to bacillary dysentery. Although amoebic dysentery is an alternative possibility, 20th century dysentery epidemics in the tropics were shown to be overwhelming due to shigellosis, once microbiological cultures were obtained and many of the putative amoeba shown to be leukocytes in the stool.8,12
Mortality is an unmistakable clinical endpoint, but descriptions of illness before death during the 19th century reflected the then current worldview of miasmic diseases, in addition to more than a tinge of racial superiority by western observers of the Polynesian and Melanesian populations.2,13,14 Pacific island populations died at high rates from infectious diseases that must have been introduced by single sailing ships that had no symptomatic sailors on board; indeed most ships had not been into another port for weeks to months before landing on a Pacific island.1,15,16 Few enteric pathogens (apart from Shigella) are capable of asymptomatic carriage as well as the great infectivity and extreme lethality described during early Pacific island epidemics. Most of the existing records were narratives from ship's captains or resident missionaries scattered across the Pacific Ocean.1,13,15 These records are reviewed recognizing that modern concerns for diagnostic and numerical precision were an unfamiliar concept to many of the people involved, Pacific islanders and their observers alike.
I thank the many unnamed colleagues, medical librarians, and archivists who have unselfishly provided data and ideas for this review.
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