Seasonal Pattern of Brucellosis in Iran: A Systematic Review and Meta-Analysis

Background and Purpose: Investigation of the seasonal pattern of brucellosis occurrence may help us to determine the etiology of disease. Seasonal pattern of brucellosis in different parts of Iran has been reported by several studies. Combining the results of these studies provide a reliable estimation of a total seasonal pattern of this zoonosis disease. This study aims to determine the overall pattern of brucellosis in Iran using meta-analysis method. Materials and Methods: Relevant evidence was identified searching the national and international databanks. Eligible articles were entered into the final meta-analysis after comprehensive review of evidence as well as quality assessment. We also calculated the standard error of the incidence according to binomial distribution formula. Because of the significant heterogeneity observed between the results, random effects model was used to combine the results. All data analyses were conducted using Stata software. Results: In total, 26 studies were entered into this systematic review including 17,311 subjects. Incidences (95% confidence intervals) of brucellosis in Iran during spring, summer, autumn and winter were estimated as of 34.4% (30.3-38.6), 33.2% (30.7-35.7), 16.4% (13.3-19.5) and 14.9% (12.7-17.1), respectively. Conclusion: This meta-analysis showed that the highest incidences of brucellosis are occurred during spring and summer, while the lowest incidences are occurred during winter and autumn.