Seasonality and Temporal Variations of Tuberculosis in the North of Iran

Background: Determining the temporal variations and seasonal pattern of diseases and forecasting their incidence can help in promoting disease control and management programs. This study was performed to determine the seasonal variation of tuberculosis and forecast its incidence until the year 2015 in one of the northern provinces of Iran. Materials and Methods: A longitudinal time series study was conducted. The study interval was from March 2001 to March 2011. The sum of daily registered cases in each month created 132 time points. The Box-Jenkins methods were used for determining the model. The best model was selected by analyzing the residuals and calculating the AIC and BIC. Results: A total of 3,313 patients were diagnosed and recorded during this time. The highest number of cases was registered in May and the difference in monthly incidence of tuberculosis was significant (P=0.007). The incidence of tuberculosis was higher in spring and summer than winter (P=0.04). According to the best model which was SARIMA (0, 1, 1)(0, 1, 1)12 , the average incidence of tuberculosis in 2015 is estimated to be 12 in 100,000 persons per year. Conclusion: The results of this study showed that in the north of Iran the incidence of tuberculosis has a cyclic pattern and the maximum incidence is in spring (May). Also, the trend of tuberculosis incidence is increasing and needs attention.