Risk Factors Associated With Time to Disease Onset Among Leprosy Contacts: A Cohort-Based Survival Analysis

Area of Science:

• Infectious Diseases
• Epidemiology
• Public Health

Background:

• Leprosy is a chronic infectious disease causing deformities, transmitted via aerosols and nasal secretions.
• Endemic in Brazil, India, and Indonesia, leprosy requires systematic contact monitoring for early detection.
• Understanding disease onset dynamics in contacts is crucial for effective control strategies.

Purpose of the Study:

• To identify risk factors for time to leprosy disease onset among contacts.
• To describe the temporal patterns of leprosy development in a historical cohort of contacts.

Main Methods:

• A retrospective cohort study followed 600 leprosy contacts for up to 5 years.
• Data collected included age, Mitsuda test, anti-PGL-I IgM serology, qPCR, BCG scar, and contact type.
• Kaplan-Meier curves and Cox proportional hazards models were used for survival analysis.

Main Results:

• 123 contacts (20.5%) developed leprosy, with highest incidence in the first 24 months.
• Positive qPCR (HR=3.67) and anti-PGL-I IgM (HR=5.48) were independently associated with earlier onset.
• Age, Mitsuda test, BCG scar, and contact type were not significant risk factors after adjustment.

Conclusions:

• Contacts with positive biomarkers (qPCR, anti-PGL-I IgM) have a significantly higher risk of developing leprosy within 5 years.
• The temporal dynamics show a peak incidence in the first two years post-diagnosis of a case.
• Targeted surveillance and timely interventions based on biomarker status can improve leprosy control.