While the overall incidence of tuberculosis (TB) in Canada is low, it is higher in certain population groups and geographic regions and exposure to people with unsuspected respiratory TB, whether patients, visitors or other health care workers (HCWs), followed by its transmission, does occur in healthcare settings. As detailed in Chapter 1: Epidemiology of Tuberculosis in Canada, populations at higher risk of active TB include Indigenous Peoples, those born or previously residing in high-TB-incidence countries (especially low- and high-human immunodeficiency virus (HIV) prevalence regions in Africa, and the Western Pacific and Southeast Asia regions), HIV-infected persons and people with a history of active TB disease. Staff and residents of homeless shelters and injection drug users may have a higher risk of TB than the general population.1,2
While some studies have indicated that HCWs are at increased risk of occupationally acquired TB,3 more recent literature from a number of low-TB-incidence countries has found that the rate of latent and active TB infection in HCWs is similar to that in the general population, particularly after adjusting for country of birth.4–10 However, occupationally acquired TB does occur.11–15 Occupational risk factors appear to be providing direct care to those with respiratory TB and participation in aerosol-generating medical procedures on individuals with infectious TB.16–18
In hospitals and other settings where people congregate and share indoor air (in the same room or via the building ventilation system), the risk of M. tuberculosis transmission can be increased if ventilation and other infection prevention and control (IPC) measures are inadequate.11,12,16,19 A number of studies have identified that TB exposures within healthcare facilities are most often due to failure to suspect or diagnose active TB and implement appropriate IPC measures.12,16,17,20–24 As a result, recommendations for the prevention of healthcare-associated transmission of M. tuberculosis to HCWs, patients/residents and visitors have been developed.25–27 Despite limited high-quality evidence on preventing TB transmission, implementation of the recommended hierarchy of IPC measures in hospitals in high-income countries was followed by a reduction in its transmission.28
This chapter reviews factors that determine or affect transmission of M. tuberculosis within hospitals and other healthcare settings, while focusing on measures to prevent transmission.
Recommendations provided are based, as much as possible, on published evidence. Evidence from randomized controlled trials, generally considered the strongest level of evidence, is limited, as this is generally not feasible when analyzing risk factors or situations involving natural exposure (e.g., TB outbreaks). As a result, all available evidence comes from observational studies, such as cohort studies and outbreak investigations. This chapter cites the evidence base from these primary studies, published literature reviews and a grey literature search of relevant international guidelines.25,27,29–32
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