Burden of Tuberculosis Infection in Household Contacts: Evidence from A Northern Kerala District

Background -Household contacts of patients with pulmonary tuberculosis (TB) are at higher risk of tuberculosis infection (TBI) because of repeated and prolonged exposure to infected patients. Early identification of TBI enables timely initiation of tuberculosis preventive treatment (TPT), through IGRA (Interferon-Gamma Release Assay). TPT will reduce the progression to active disease and contribute to national TB elimination strategies.Methods – A cross-sectional observational study was conducted among household contacts of pulmonary TB patients diagnosed in two tuberculosis unit of northern Kerala between 2024 and 2025. All those aged above 5yrs who are household contacts of Pulmonary TB were enrolled after obtaining informed written consent. All Participants subjected to IGRA (QuantiFERON-TB Gold Plus)testing. IGRA-positive individuals were further evaluated to exclude active TB. Clinical, Sociodemographic, comorbidities, substance abuse, smoking history, , immunosuppression and overcrowding were documented using a semi-structured questionnaire. Data analysis was performed using SPSS software, and associations were assessed using chi-square tests (p < 0.05 considered significant).Results – Of 204 household contacts screened, 93 were IGRA-positive yielding a TBI prevalence of 45.6%. Diabetes mellitus was significantly associated with IGRA positivity (79.3%; p = 0.023). No statistically significant associations were observed between IGRA positivity and sex (p = 0.977), age group (p = 0.55), smoking history (p = 0.633), symptom status (p = 0.458), comorbidity profile (p = 0.116), substance abuse (p = 0.346), or overcrowding (p = 0.88).Conclusion – Nearly one in two household contacts of pulmonary TB patients had evidence of tuberculosis infection, more than double that reported in the general Kerala population. Diabetes mellitus was independently associated with higher IGRA positivity These findings strongly support IGRA-based screening of all household contacts, and prompt TPT initiation, particularly among individuals with diabetes mellitus.