The incidence and distribution of scrub typhus in North Queensland.

Abstract

SummaryIn the four years 1951–1955, 199 cases or probable cases of scrub typhus were recognized in North Queensland. The geographical distribution was discontinuous along the Pacific Coast from near Thursday Island (10.6° S.), where cases have not previously been reported, to Mackay (21.1° S.). All but four occurred between Cooktown (15.5° S.) and Ingham (18.7° S.). Most cases arose in a narrow belt close to the sea, and all within 40 miles of it. Some arose on the Atherton Tableland at an elevation of 2000 to 3000 feet.The scrub typhus region has an abundant rainfall and high humidity. Like the potential rain forest region, it is approximately bounded by the 60‐inch isohyet. The mean annual temperature in the scrub typhus region ranges from 80.7° F. at Thursday Island to 68.1° F. at Atherton. The boundary of the region is not related to any isotherm.The existence of foci of high and persisting endemicity, noted in other countries, is evident also in North Queensland. They offer opportunities for intensive ecological studies and for evaluation of preventive measures.The highest monthly incidence was from March to July. The seasonal variation appears to be determined primarily by the rainfall—the wet season is from January to April—but modified by the occupational or recreational activities that take people into endemic foci.Infection was associated with occupation in about 65 %—mainly timber‐cutting, scrub‐clearing and fruit‐farming—and in 18% with recreation. In 17% the significant activity was not defined.