Some observations on the current plague outbreak in the Republic of Vietnam.

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Abstract
The incidence of bubonic plague, with occasional limited outbreaks of pneumonic plaque, has reached alarming proportions since 1962 in the Republic of Vietnam, some 13,263 cases being reported during this period. The disease shows distinct seasonal tendencies, the majority of cases occurring during the hot, dry weather just prior to the onset of monsoon rains. Three species of mammals, Rattus rattus, R. exulans, and Suncus murinus are all, to an equal extent, incriminated as reservoir hosts of the disease in Vietnamese cities. The vector fleas, Xenopsylla cheopis, in 2 major plague foci are, by WHO [World Health Organization] cri-teria, resistant to DDT, which has been extensively used in this area in the past. Extensive application of DDT dusts has apparently failed to control the disease. Diazinon, however, an insecticide to which fleas are, by test, susceptible, has achieved rapid control in at least 2 foci. Vaccination with a living plague vaccine (EV strain) appears to markedly reduce the incidence of disease in the Vietnamese, who are the population group most affected. Americans living in the same environment enjoy a unique freedom from the disease, a result credited to the killed vaccine, which all receive, and a much higher level of environmental sanitation. A rather dangerous potential for dissemination of both bubonic and pneumonic forms of plague from Vietnam exists.