Abstract
            Introduction: Tuberculosis (TB) is one of the most common and lethal infectious diseases.  
  Objectives: Due to the impact of biological, behavioral, socio-economic factors on the incidence of TB and  the risks of the disease, we aimed to investigate the factors affecting TB in TB patients in Semnan.  
  Patients and Methods: All patients with confirmed TB, who were referred to primary healthcare centers in  Semnan for receiving medication, enrolled in the study (2012 to 2016). Data collected from clinical records  and in-person interviews. The questionnaire consisted of two parts; the first part was demographic data and  the other was related to the risk factors for TB.  
  Results: The household crowding index was 1.86 ± 0.88. Most of patients (48.1%) were elderly (≥60 years  old), female (59.7%), housewife (48.1%), had a pre-diploma education (63.6%), low-monthly income  (62.3%) and married (63.6%). Around13.0% had diabetes. 20.8% drug abuser, 16.9% cigarettes and  tobacco smokers, and 1.3% consumed alcoholic beverages. Besides, 40.3% were Afghans and 1.3% had  the Pakistani nation.  
  Conclusion: Identifying and controlling the social, geographical and biological factors affecting the  incidence and mortality of TB in different regions can help to formulate appropriate strategies for achieving  global goals. These factors differ among native and non-native population.