Effective Reproduction Number of Smear-Positive Pulmonary Tuberculosis in Iran: A Registry-Based Study (2011-2021)

Area of Science:

• Epidemiology
• Public Health
• Infectious Disease Dynamics

Background:

• Tuberculosis (TB) is a significant public health concern in Iran, particularly smear-positive pulmonary tuberculosis (SPPTB), due to its high transmissibility.
• Understanding the effective reproduction number (R) and patient characteristics is vital for effective TB control strategies.

Purpose of the Study:

• To assess the effective reproduction number (R) of SPPTB in Iran between 2011 and 2021.
• To analyze SPPTB patient demographics, initial bacillary load, diagnostic delays, and geographical distribution.

Main Methods:

• A historical cohort study design was employed.
• A time-dependent method was utilized to estimate the effective reproduction number (R).
• Monthly data from the national TB registry spanning 2011–2021 were analyzed.

Main Results:

• SPPTB incidence rates in Iran decreased from 2011 to 2021, with 50,909 cases reported.
• Diagnosis delays were observed, with 29.1% diagnosed within one month and 44.5% experiencing a one-to-three-month delay.
• Significant regional variations in TB transmission were found, with Sistan and Baluchestan, Golestan, Guilan, Khuzestan, Tehran, and Khorasan Razavi showing the highest R values. A decreasing trend in R was noted across provinces from 2011 to 2020.

Conclusions:

• Effective reproduction numbers generally declined from 2011–2020 but saw a moderate increase post-COVID-19, necessitating targeted public health interventions.
• Despite a national decline in SPPTB incidence, persistent TB management is crucial in high-incidence provinces like Sistan and Baluchestan, Golestan, Guilan, Khuzestan, Tehran, and Khorasan Razavi.