What is a Hotspot Anyway?

The importance of spatial clusters, or “hotspots,” in infectious disease epidemiology has been increasingly recognized, and targeting hotspots is often seen as an important component of disease-control strategies. However, the precise meaning of “hotspot” varies widely in current research and policy documents. Hotspots have been variously described as areas of elevated incidence or prevalence, higher transmission efficiency or risk, or higher probability of disease emergence. This ambiguity has led to confusion and may result in mistaken inferences regarding the best way to target interventions. We surveyed the literature on epidemiologic hotspots, examining the multitude of ways in which the term is used; and highlight the difference in the geographic scale of hotspots and the properties they are supposed to have. In response to the diversity in the term's usage, we advocate the use of more precise terms, such as “burden hotspot,” “transmission hotspot,” and “emergence hotspot,” as well as explicit specification of the spatiotemporal scale of interest. Increased precision in terminology is needed to ensure clear and effective policies for disease control.