SEASONALITY PATTERN OF TUBERCULOSIS IN IRAN

Awareness regarding incidence pattern of disease is an important issue for researchers. To explore seasonal pattern of TB in Iran we decided to do this study. This study have been done as an ecologic study. all notified TB cases during 1997 to 2001 have been included in this study. all data have been processed and analyzed by the Cosinor analysis method. We found 59756 registered TB cases during above mentioned years. TB in this 5 year period has seasonal pattern (amplitude=11.73%, acrophase=13 June(85.23), p<0.000). Frequency of TB cases evaluated by sex in this model and found that there is seasonality by sex too (p<0.000), but different amplitudes found for female and male(13.35%, 10.5%) and point estimate of acrophase for them were consequently 18 June and 8 June. When we evaluate this pattern among smear positive and smear negative cases found that smear positives have seasonal pattern (p<0.000). Association of TB frequencies in quarters and mean temperature of each quarter have been evaluated by ANOVA in different 4 temperature groups(p< 0.020), and a significant difference have been found between 10-20 and 20-30 temperature groups(p<0.051). According to this study there is a seasonal pattern in TB notification (incidence) in Iran which should be notified in population based studies and surveys in this regards. Comments: We recommend performing more studies on patterns of pulmonary disease, other relevant factors on TB involvement and also laboratory circulation to clarifying cause of existing seasonality