Transmission of Tuberculosis Among Illicit Drug Use Linkages

Tuberculosis (TB) is the leading infectious disease killer globally and leading cause of death in persons with HIV. The most effective way to reduce TB incidence and mortality is to interrupt transmission. This requires finding and treating individuals with TB disease early, including those with subclinical disease. Molecular epidemiologic studies and mathematical models have shown that the primary approach to case finding-household contact tracing-identifies only 8-19% of transmissions in high TB and TB/HIV burden settings. Thus there is a clear need to identify new groups and settings where TB transmission occurs. Spatial clustering of individuals with higher rates of progression from infection to disease, such as those with HIV and malnourishment, can also form transmission hotspots. Illicit drug (i.e., methamphetamines, crack/cocaine, opiates) users have higher TB infection prevalence and disease incidence compared to non-users, likely due to significant within-group transmission and/or clustered vulnerability. Increased transmission among people who use illicit drugs (PWUD) could result from creation of more efficient TB transmitters, increased close contact among transmitters, increased rates of primary progression from infection to disease among contacts, or a combination. Interrogation of illicit drug user networks for TB transmission, therefore, holds great potential as a target for early case identification and linkage to treatment, with potential benefit for halting transmission to the broader population.