Tuberculosis outbreak in marijuana users, Seattle, Washington, 2004.

Matching Mycobacterium tuberculosis isolates were noted among 11 young tuberculosis patients socially linked through illicit drug-related activities. A large proportion of their friends, 14 (64%) of 22, had positive tuberculin skin-test results. The behavior of "hotboxing" (smoking marijuana inside a closed car with friends to repeatedly inhale exhaled smoke) fueled transmission.