RESUMO
AIM: To analyze changes in prevalence and seasonality of diarrhea morbidity and mortality and to evaluate the impact of rotavirus disease among Mexican children younger than 5 years old. METHODS: Diarrhea surveillance was performed from 1990 to 2002. Rotavirus testing was performed on stool specimens from 1996 to 2002. Data were obtained from different surveillance systems considering a nationwide representation in Mexico. Diarrhea morbidity and mortality rates were analyzed against time to determine trends or seasonal patterns. RESULTS: Improvement of surveillance for all diarrhea episodes denoted an initial morbidity increase from 1995 to 1999, followed by a decrease by 2002, without any seasonal pattern. However, from 1990 to 1995, morbidity for severe diarrhea decreased 63%. From 1996 to 2002, 62-68% of severe diarrhea episodes occurring during the fall-winter season (FWS) were rotavirus-positive compared with 6-12% in the spring-summer season (SSS). From 1990 to 2002, diarrhea mortality decreased 84%. Higher mortality rates for children younger than 1 year old coincided precisely during the FWS, annually. Both severe diarrhea episodes and diarrhea deaths denoted a changing seasonal pattern. In 1990-1991, 2 waves of increased diarrhea activity occurred. The increase in SSS was much more pronounced than that in FWS. From 1992 to 1995 for severe diarrhea and from 1993 to 2002 for diarrhea deaths, the SSS frequencies subsequently reduced, whereas the FWS peaks remained annually. CONCLUSIONS: A significant reduction in morbidity and mortality of severe diarrhea has occurred from 1990 and 2002 in Mexican children younger than 5 years old. This is a consequence of preventive programs initiated for cholera control since 1991, which had greater impact on SSS diarrhea and limited response for FWS diarrhea, when rotavirus is mainly present. Currently rotavirus diarrhea requires new prevention strategies and specific control measures, such as a specific national vaccine program.