Detection, survival and infectious potential of Mycobacterium tuberculosis in the environment: A review of the evidence and epidemiological implications

Much remains unknown about Mycobacterium tuberculosis transmission. Seminal experimental studies from the 1950s demonstrated that airborne expulsion of droplet nuclei from an infectious tuberculosis patient is the primary route of transmission. However, these findings did not rule out other routes of M. tuberculos is transmission. We reviewed historical scientific evidence from the late 19 th and early 20 th century and contemporary studies investigating the presence, persistence, and infectiousness of environmental M. tuberculosis . We found evidence – both experimental and epidemiological – supporting the presence and viability of M. tuberculosis in multiple natural and built environments for months to years, presumably following contamination by a human source. Further, several studies confirm M. tuberculosis viability and virulence in the environment using guinea pig and mouse models. Most of this evidence was historical; however, several recent studies have reported consistent findings of M. tuberculosis detection and viability in the environment using modern methods. Whether or not M. tuberculosis in environments represents an infectious threat to humans, it may represent an untapped source of data with which to further understand M. tuberculosis transmission. We discuss potential opportunities for harnessing these data to generate new insights into tuberculosis transmission in congregate settings.