Spatial and temporal distribution of cholera in Ecuador between 1991 and 1996

Abstract

Background: The seventh pandemic of cholera affected South America in 1991 after a century of absence. Favoured by local conditions, the epidemic of cholera in Ecuador had a rapid impact. The epidemic of cholera evolved with temporal and geographical variations. Methods: The temporal and geographical variations of cholera in Ecuador between 1991 and 1996 have been analysed. The Ecuadorian epidemiological surveillance system is a semi-active one based on obligatory weekly declarations. A geographical representation of annual impact rate has been made. Using a smoothing technique by cross-validation, time curves were identified and spatial diffusion was studied by cartography. Results: In 1991 and 1992, cholera in Ecuador evolved in an epidemic mode with two explosive epidemic peaks. Cholera then entered a phase of regression. The disease spread from two main epicentres, one in the South (El Oro, Guayas, Los Rios) and the other in the North (Esmeraldas and Imbabura). These focal outbreaks spread to neighbouring provinces during the peak outbreaks between 1991 and 1993. Conclusion: This study demonstrated that the epidemic spread from the affected provinces in the South and the North of the country.