Exploratory space-time analysis of reported dengue cases during an outbreak in Florida, Puerto Rico, 1991-1992.

ABSTRACT

PIP: Through use of the Geographic Information System (GIS), the spatial and temporal distributions of dengue cases reported during a 1990-91 outbreak in Florida, Puerto Rico, were reviewed. The GIS, a computer system that can store, assemble, manipulate, and analyze geographically referenced material, offers a new approach to the study of disease patterns. A total of 377 dengue cases were identified from a laboratory-based dengue surveillance system and georeferenced by their residential addresses on digital zoning and US Geological Survey topographic maps. Weekly case maps were generated for the period June-December 1991, when 94.2% of dengue cases were reported. The epidemic's temporal evolution was rapid, affecting a wide geographic region within 7 weeks of the first reported cases of the season. Cases were reported in 217 houses, 56 (25.8%) of which had 2-6 cases each. Both K-function analysis, and the Barton and David-Knox tests, revealed significant case clustering within individual households over a period of 3 days or less. In general, however, cases had spatial pattern characteristics similar to the population pattern as a whole. The rapid spatial and temporal progress of dengue cases within the community suggests that vector control measures (e.g., source reduction) should be applied to the entire municipality, rather than to the areas immediately surrounding houses of reported cases.