Preventing Transmission

Only active pulmonary or laryngeal tuberculosis is contagious. Latent tuberculosis is not contagious, and extrapulmonary tuberculosis is not contagious, unless the infectious material is mechanically aerosolized (e.g., use of bone saws with tuberculous bone disease).  Mycobacterium TB is sensitive to ultraviolet light, and is not transmitted by contact with skin or mucus membranes.

Key Prevention Elements

The key elements in preventing transmission from active contagious cases include:
  • Masking of patient (surgical mask, not N-95) when necessary, in order to catch respiratory droplets before they dry and become aerosolized respiratory nuclei.
  • Use of N-95 respirators or PAPR with HEPA filters for health care personnel providing treatment to contagious cases.
  • Engineering to reduce concentration of infectious particles (ventilation with high rate of air exchange, treatment with UV, negative pressure to prevent airborne spread beyond patient's room). Outdoor exposure is not a risk, as UV and dilution are effective in reducing concentration of viable MTB to safe levels.
For details, see Guidelines for Preventing the Transmission of Mycobacterium Tuberculosis in Health-Care Settings, 2005. MMWR 2005;54(No. RR-17) (PDF).