Seasonality of Pulmonary Tuberculosis in Sousse (Tunisia).

Introduction: Seasonal variation of Pulmonary tuberculosis (TB) has attracted the attention in several regions of the world.

Aim: To explore the relationship between variations of mean meteorological parameters (temperature, atmospheric pressure, relative humidity and duration of sunshine) and the occurrence of cases of pulmonary TB.

Methods: This is a retrospective descriptive study of two-time series (meteorological data, case of pulmonary TB) from 1th January 2010 to 31th December 2014.Meteorological data were collected throughout the 5-year period.

Results: We collected 180 cases confirmed by direct examination. The relationship between seasonality and the occurrence of TB cases was addressed in two ways considering either the date of the bacteriological diagnosis or the date date of onset of symptoms of TB as the date of the census of cases. Taking into account the date of bacteriological diagnosis, it appeared that spring (33.7%) and summer (25.9%) had the most days with positive diagnosis (p = 0.012). However, considering the date of onset of symptoms of TB , it appeared that winter (34.2%) and spring (28%) had the most days with positive diagnosis with a significant difference. The comparison of the mean of meteorological parameters between days with and without bacteriological diagnosis showed that only the mean duration of sunshine was significatively associated with more cases(p=0.002). This same comparison between the days with and without TB according to the date of onset of symptoms of TB showed significant difference only for mean temperatures which were lower  during the days when patients présented symptoms of TB (p=0.013).

Conclusion: Our results have highlighted the possible implication of meteorological parameters in the occurrence of pulmonary TB cases.