Numerous recent reports have detailed outbreaks of tuberculosis in hospitals and other
congregate settings. The characteristics of such settings, including high concentrations of infectious patients and immunocompromised hosts, the potential for sustained daily contact for weeks and often months, and improper precautions taken
for protection, make them well suited for tuberculosis transmission. However, community-based
outbreaks, which are the source of much public concern, have not been reviewed since 1964, when
109 community outbreaks were examined. Since few of the characteristics of institutional settings
are present in the community, the lessons learned may not be applicable to community-based out-breaks. Furthermore, recent studies with analysis by restriction fragment length polymorphisms
have documented unexpectedly high rates of primary disease in certain urban communities, suggesting that our understanding of community-based transmission may be incomplete. We reviewed all reported community-based outbreaks of tuberculosis occurring in the last 30 years to
assess the basis of our current understanding of community-based transmission. More than 70 out-breaks were identified, with schools being the most common site. In most, a delay in diagnosis,
sustained contact with the index case, inadequate ventilation, or overcrowding was contributory.
We conclude that community-based outbreaks of tuberculosis continue to occur and that well-established risks contribute to most outbreaks. Many outbreaks can be prevented or limited by
attention to basic infection control principles.
(Arch Intern Med. 1996;156:1053-1060)