Large Tuberculosis Outbreaks - United States, 2017-2023

Area of Science:

• Epidemiology
• Public Health
• Genomic Surveillance

Background:

• Tuberculosis (TB) remains a significant global health concern.
• Large TB outbreaks pose unique challenges to public health surveillance and control.
• Understanding the characteristics of individuals involved in large TB outbreaks is crucial for targeted interventions.

Purpose of the Study:

• To identify and characterize large tuberculosis outbreaks in the U.S. between 2017-2023.
• To compare demographic and risk factors of individuals in large outbreaks versus sporadic TB cases.
• To evaluate the role of contact tracing in identifying outbreak-related TB cases.

Main Methods:

• Analysis of national genomic and TB case surveillance data from 2017-2023.
• Identification of large outbreaks defined as 10 or more related TB cases within a 3-year period.
• Comparison of characteristics between individuals in large outbreaks and other TB patients.

Main Results:

• 50 large TB outbreaks involving 1,092 cases were identified across 23 states.
• Individuals in large outbreaks were more frequently U.S.-born (79%) and reported higher rates of substance use (27%), homelessness (9%), and incarceration (11%).
• Contact tracing identified approximately one-fourth of outbreak cases, often with fewer markers of infectiousness compared to cases found through other methods.

Conclusions:

• Large TB outbreaks are associated with specific demographic and social risk factors, including U.S. birth, substance use, homelessness, and incarceration.
• Contact tracing may facilitate earlier diagnosis of TB in outbreak settings.
• Sustained public health capacity for TB outbreak detection, prevention, and response is essential, particularly addressing barriers faced by vulnerable populations.