COMMUNITY-BASED OUTBREAKS OF TUBERCULOSIS

Numerous recent reports have detailed outbreaks of tuberculosis in hos pitals and other congregate settings, The characteristics of such sett ings, including high concentrations of infectious patients and immunoc ompromised 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-bas ed outbreaks, which are the source of much public concern, have not be en reviewed since 1964, when 109 community outbreaks were examined. Si nce few of the characteristics of institutional settings are present i n the community, the lessons learned may not be applicable to communit y-based out-breaks. Furthermore, recent studies with analysis by restr iction fragment length polymorphisms have documented unexpectedly high rates of primary disease in certain urban communities, suggesting tha t our understanding of community-based transmission may be incomplete. We reviewed all reported community-based outbreaks of tuberculosis oc curring in the last 30 years to assess the basis of our current unders tanding 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 ventil ation, or overcrowding was contributory, We conclude that community-ba sed outbreaks of tuberculosis continue to occur and that well-establis hed risks contribute to most outbreaks. Many outbreaks can be prevente d or limited by attention to basic infection control principles.