Dengue fever is an arboviral disease typical of the tropics that can be life-threatening and if not controlled properly may result in an epidemic. The absence of an effective vaccine makes strategies to prevent the virus transmission the most effective means of control. The planning of such strategies, however, is difficult due to the constant movement of individuals and mosquito host (Aedes aegypti). In this paper, the spatial and temporal relations that might exist between infected individuals during a dengue-epidemic year are explored. This research is motivated in that a deep understanding of potential transmission patterns between individuals might lead to a better design and planning of control strategies. A GIS-based Health Exploratory AnaLysis Tool (HELP) is used to compute space-time relationships by means of spatial K-function, kernel density, space-time K-function and linking pairs of cases within significant time and space intervals. Significant clustering was observed at a scale of 50 meters and 750 meters, respectively while temporal significance was determined at two days and five to eight days. While an increase of cases occurs in the months following severe droughts due to an El Niño phenomenon, the location of clusters remains relatively stable. These are observed near areas where potential habitats for the mosquito exist such as storm drains, hard surfaces where water accumulates (e.g., vases, containers), but also in poorer neighborhoods. The results from the spatial analysis provide valuable information for health care managers to take preventive actions at the municipality level.

El propósito de la investigación fue medir y comparar las incidencias del hepatoma (carcinoma hepatocelular, CHC), la cirrosis hepatocelular y la hepatitis B en la ciudad de Cali y clasificar las comunas de la ciudad según el riesgo de infección y sus complicaciones crónicas, para así establecer prioridades para las comunas más vulnerables y orientar eficientemente las acciones de promoción y prevención. No había estudios similares que expresaran la correlación y dinámica entre estos tres eventos en la región de las Américas. Association among hepatoma, cirrosis and hepatitis B incidence in CaliThe purpose of the study was to measure cirrhosis. hepatoma and hepatitis B incidences in Cali, Colombia, and compare them according to geographical area, local health systems (SILOS) and neighborhoods. The coefficients r were high and statistically significant according to SILOS, as follows: CHC-CIRROSIS, r.0.82; IC: 0.03-0.98 and Pc0.05; HB-CIRROSIS, r=0.89; IC: 0.3-0.99 and Pc0.05; HB-CHC, r=0.9; IC: 0.03-0.99 and P<0.05. With respect to neighborhoods. the coefficient r was high and significant between CHC and cirrhosis, r=0.65; IC: 0.29-0.85 and Pc0.05, while r were low and not statiscally significant between hepatitis E and the other iwo diseases: HE-CIRROSIS, r=0.22; IC: 0.02-0.61; HB-CHC, r=0.42: IC: 0.03-0.73 and P>0.05. These results suggest an association among the events described for the three diseases and allow us to priorize the geographic areas for promotion and prevention programs. The cost-effectivity study in the five neighborhoods with the highest risk, based on New York City's su~eillance and vaccination program, 1987-1988, showed that immunization is seventy five times better than treatment of liver cronic diseases.