Pulmonary Tuberculosis Seasonality Survey in Fars Province, South of Iran

Background: Some studies show tuberculosis (TB) seasonal pattern. There are only two reports addressing TB seasonal pattern in Iran. Objectives: The current retrospective analysis aimed at determining the seasonal distribution pattern of all registered pulmonary TB cases over the recent six years in Fars province of Iran. Methods: All patients with pulmonary TB in Fars province diagnosed from 2006 to 2011 were investigated in terms of gender, age, and the month of definitive diagnosis. Patients with clinical symptoms suggestive of pulmonary TB with at least one documented positive culture or smear for acid-fast bacilli were included. Results: A total of 934 patients with pulmonary TB with a mean age of 44.3 ± 21 years were studied, of whom 319 (42.2%) were male. The highest proportion of patients were diagnosed in May (10.7%) and June (10.2%) (P = 0.033). More than 29% of the TB incidents occurred during spring. The proportion of patients presenting in spring decreased from 39.7% in 2006 to 28.4% in 2011. Similarly, percentage of patients recorded in summer significantly decreased during the study (P = 0.008). Conclusions: Pulmonary TB is a seasonal disease in Fars province with peak incidence in warm seasons independent of patients’ age and gender though seasonal fluctuations decreased over the study period.