Reproduction number, turning point, total number of cases and impact of interventions during dengue outbreak in Playa municipality, La Habana city

Abstract

Introduction: The magnitude of basic reproduction ratio R0 of an epidemic can be estimated in several ways. R0 is the most important quantity in the study of epidemic, especially comparing the effects of control strategies. The main objective was to estimate the R0 and the maximum case number to evaluate the impact vector control interventions. Methods: The research was conducted in all Primary Health Care Areas of the municipality of Playa, La Habana City, during 2001-2002. Outbreak dengue control actions in Playa were stepped up in three phases. First, the health authorities intensified actions in a radius of 100m² around houses of confirmed cases. Second, municipality authorities intensified the control actions with human recourses and support from other municipalities in La Habana. Third, an intensive campaign started in La Habana City, including Playa, involving the head of state, governement, political bodies at all levels, and community organizations, the estimation of R0 was derived for each health area using the Richards model, considered the cummulative infected population size. Result: We estimate an overall reproduction number of 3.25 for the whole municipality. The R0 by health area ranges from 2 to 7. The turning point was around 13 and 14 for six areas, independent of the values for R0 and the moment when the transmission started in the area. The R0 were higher in areas with higher values of Aedes larval index. The areas where transmission started after the second phase of control actions reported the lowest attack rates. Conclusion: The model used enabled us to estimate the R0, final size and the turning point of the dengue outbreak and compare the areas to evaluate the impact vector control interventions.