The transmission of tuberculosis (TB) in healthcare facilities is an important public health concern. Factors that contribute to nosocomial TB transmission include deterioration of the public health infrastructure, the human immunodeficiency virus (HIV) epidemic, and inadequate infection control measures in healthcare facilities. Careful infection control measures can reduce healthcare-associated transmission of TB and improved public health TB control programs have reduced the incidence of TB in the community as a whole .
Issues related to control of TB transmission will be reviewed here. Other issues related to TB are discussed in detail separately. (See related topics.)
Person-to-person transmission of tuberculosis (TB) occurs via inhalation of droplet nuclei (airborne particles 1 to 5 microns in diameter). Coughing and singing facilitate formation of droplet nuclei [2-6]. Individuals with active untreated pulmonary or laryngeal disease are contagious, particularly when cavitary disease is present or when the sputum is acid-fast bacilli (AFB) smear positive. Patients with sputum smear-negative, culture-positive pulmonary TB can also transmit infection; among 844 secondary cases of TB in the Netherlands between 1996 and 2004, 13 percent were attributable to transmission from index patients who were smear negative . One study suggested that a short time to growth on culture (<9 days), as a potential marker of greater disease burden, was associated with a higher risk of transmission regardless of AFB smear results . Culture of cough aerosols for Mycobacterium tuberculosis may also be useful for prediction of transmission . (See "Microbiology and pathogenesis of tuberculosis".)
Procedures that can result in the dispersal of droplet nuclei have been associated with an increased risk of TB transmission. These include endotracheal intubation, bronchoscopy, sputum induction, aerosol treatments (eg, pentamidine), irrigation of a tuberculous abscess, and autopsy .
Isolated extrapulmonary tuberculosis is not contagious, although such patients require careful evaluation for pulmonary or laryngeal TB, since patients with both extrapulmonary disease and pulmonary disease are contagious. Immunocompromised patients with extrapulmonary TB should be presumed to have pulmonary TB until proven otherwise with negative sputum samples, even if chest radiography is normal.