Tuberculosis transmission and control
- Kimon C Zachary, MD
Kimon C Zachary, MD
- Assistant Professor of Medicine
- Harvard Medical School
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 "Natural history, 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.
- Jensen PA, Lambert LA, Iademarco MF, et al. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care settings, 2005. MMWR Recomm Rep 2005; 54:1.
- Sepkowitz KA. How contagious is tuberculosis? Clin Infect Dis 1996; 23:954.
- Loudon RG, Spohn SK. Cough frequency and infectivity in patients with pulmonary tuberculosis. Am Rev Respir Dis 1969; 99:109.
- Loudon RG, Roberts RM. Droplet expulsion from the respiratory tract. Am Rev Respir Dis 1967; 95:435.
- Loudon RG, Roberts RM. Singing and the dissemination of tuberculosis. Am Rev Respir Dis 1968; 98:297.
- BATES JH, POTTS WE, LEWIS M. EPIDEMIOLOGY OF PRIMARY TUBERCULOSIS IN AN INDUSTRIAL SCHOOL. N Engl J Med 1965; 272:714.
- Tostmann A, Kik SV, Kalisvaart NA, et al. Tuberculosis transmission by patients with smear-negative pulmonary tuberculosis in a large cohort in the Netherlands. Clin Infect Dis 2008; 47:1135.
- O'Shea MK, Koh GC, Munang M, et al. Time-to-detection in culture predicts risk of Mycobacterium tuberculosis transmission: a cohort study. Clin Infect Dis 2014; 59:177.
- Jones-López EC, Namugga O, Mumbowa F, et al. Cough aerosols of Mycobacterium tuberculosis predict new infection: a household contact study. Am J Respir Crit Care Med 2013; 187:1007.
- Dharmadhikari AS, Mphahlele M, Stoltz A, et al. Surgical face masks worn by patients with multidrug-resistant tuberculosis: impact on infectivity of air on a hospital ward. Am J Respir Crit Care Med 2012; 185:1104.
- Moran GJ, Barrett TW, Mower WR, et al. Decision instrument for the isolation of pneumonia patients with suspected pulmonary tuberculosis admitted through US emergency departments. Ann Emerg Med 2009; 53:625.
- Welbel SF, French AL, Bush P, et al. Protecting health care workers from tuberculosis: a 10-year experience. Am J Infect Control 2009; 37:668.
- Chaisson LH, Roemer M, Cantu D, et al. Impact of GeneXpert MTB/RIF assay on triage of respiratory isolation rooms for inpatients with presumed tuberculosis: a hypothetical trial. Clin Infect Dis 2014; 59:1353.
- Lippincott CK, Miller MB, Popowitch EB, et al. Xpert MTB/RIF assay shortens airborne isolation for hospitalized patients with presumptive tuberculosis in the United States. Clin Infect Dis 2014; 59:186.
- Centers for Disease Control and Prevention: Tuberculosis (TB) http://www.cdc.gov/tb/amplification_tests/amplification_tests.pdf (Accessed on January 20, 2008).
- Centers for Disease Control and Prevention (CDC). Updated guidelines for the use of nucleic acid amplification tests in the diagnosis of tuberculosis. MMWR Morb Mortal Wkly Rep 2009; 58:7.
- Cepheid. Xpert MTB/RIF assay [package insert]. Cepheid, Sunnyvale, CA 2015. Available at: www.cepheid.com/mtbrif-pi (Accessed March 2, 2015).
- Division of Microbiology Devices, Office of In Vitro Diagnostics and Radiological Health, Center for Devices and Radiological Health, Food and Drug Administration, Centers for Disease Control and Prevention (CDC). Revised device labeling for the Cepheid Xpert MTB/RIF assay for detecting Mycobacterium tuberculosis. MMWR Morb Mortal Wkly Rep 2015; 64:193.
- Noble, RC. Infectiousness of pulmonary tuberculosis after starting chemotherapy: review of the available data on an unresolved question. Am J Infect Control 1981; 9:6.
- Tokars JI, McKinley GF, Otten J, et al. Use and efficacy of tuberculosis infection control practices at hospitals with previous outbreaks of multidrug-resistant tuberculosis. Infect Control Hosp Epidemiol 2001; 22:449.
- Sutton PM, Nicas M, Harrison RJ. Tuberculosis isolation: comparison of written procedures and actual practices in three California hospitals. Infect Control Hosp Epidemiol 2000; 21:28.
- Anger HA, Proops D, Harris TG, et al. Active case finding and prevention of tuberculosis among a cohort of contacts exposed to infectious tuberculosis cases in New York City. Clin Infect Dis 2012; 54:1287.
- TB TRANSMISSION
- TB INFECTION CONTROL
- Outpatient and emergency room management
- Inpatient management
- - Clinical evaluation
- - Isolation rooms
- - Use of masks
- - Laboratory evaluation
- - Discontinuation of isolation
- - Discharge planning
- Infection control compliance
- TB surveillance
- CONTACT INVESTIGATION
- INFORMATION FOR PATIENTS