[Analysis of the monthly incidence of cutaneous leishmaniasis in Ceará (Brazil) between 1986 and 1990].

To determine the value of an epidemiological surveillance system, we evaluated the incidence rate and trends of American Cutaneous Leishmaniasis (ACL) in three health districts of Ceara state, Brazil. We used a retrospective time series analysis of ACL notifications in Ceara state between 1986 and 1990. The trend of this endemic/epidemic disease was analysed by using three types of modeling on the moving average graph: a linear, linear periodic and non linear periodic model. The study samples consisted of the 14,615 cases of ACL notified in Ceara state between 1986 and 1990. Males accounted for 54% of cases. Age was between 1 month and 19 years in 42% of cases. Most cases (81%) were diagnosed on clinical grounds only. After calculation of the moving average and application of a linear regression model to these means, the trend analysis revealed that 1) there was a significant trend towards an increase in two of the three health districts, with correlation coefficients of 0.31 and 0.49 (Student's t test = 2.24 and 3.88) and a significant trend towards a decrease in the remaining district (correlation coefficient = 0.51, t = 4.1). The linear periodic model showed a cyclic representation with a 36-month period and a base of 241. The non linear periodic model showed a cycle of 32 months and a base of 241, and was a better representation of the disease variations. Despite the limited study period, it appears that the 32-month cycle could be attributed to meteorological conditions. Field studies are underway to determine the precise causes of this periodicity.