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Definition.— A mosquito - conveyed specific fever occurring usually as a rapidly spreading epidemic and, in typical cases, characterized by a suddenly developed primary fever of about three days' duration, succeeded by a period of apyrexia— actual or relative —and this again by a milder secondary fever accompanied by a rubeoloid eruption. Throughout the febrile stages, and often subsequently, severe rheumatic-like pains are 9 prominent symptom. The disease in its active form lasts about a week and is attended with little, if any, mortality.

Geographical distribution and mode of spread.— Most parts of the tropical world have been visited at one time or another by dengue. From a study of the dates of the various epidemics, it would seem that there is a tendency for it to assume pandemic characters about once in every twenty years. Perhaps of all places in the world it is most frequently met with in the West Indies.

Recently dengue has appeared in Syria, Asia Minor, on the Ægean shores of Greece and Turkey, and in North Queensland, Australia. Early in the last century it was seen in America, as far north as Charleston and Philadelphia in the United States, and as far south as São Paulo in the Brazils.

Like other specific communicable diseases, dengue tends to advance along trade routes and lines of communication. Thus, starting from Zanzibar, the epidemic of 1870-73 first reached Aden. Thence it travelled to Suez on the one side and to India on the other. Passing to Singapore, it followed the trade routes to