Trends in the prevalence of Chagas' disease among first-time blood donors in São Paulo, Brazil.

BACKGROUND: Screening of blood donors for Chagas' disease is mandatory in Brazil. Data about the prevalence of Chagas' disease among first-time blood donors has not been previously reported. The objective of this study was to report the trends in the prevalence of Chagas' disease among first-time blood donors in São Paulo, Brazil according to gender, age, and type of donation.

STUDY DESIGN AND METHODS: The data was obtained at Fundação Pró-Sangue/Hemocentro de São Paulo during the period of 1996 to 2001. Samples were considered positive if they were reactive to the three serologic tests used at screening (indirect immunofluorescence, indirect hemagglutination, and EIA).

RESULTS: The prevalence of Chagas' disease was two times higher among replacement blood donors than among altruistic donors (52 vs. 25 cases/10,000). The overall prevalence among blood donors decreased at a rate of 1.86 cases per 10,000 per year. An increase in the proportion of altruistic donors and a decrease in the prevalence primarily among younger donors were observed.

CONCLUSION: The prevalence of Chagas' disease is decreasing in the São Paulo population. Differences in the socioeconomic level between altruistic and replacement donors may be the reason for the differences in the prevalence among these groups. It will be important to target for study the population of young seroreactive blood donors to better understand how new infections are occurring.