Community-Based Outbreaks of Tuberculosis

Abstract

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 outbreaks. 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 outbreaks 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.

Dynamics of Tuberculosis: The effect of Direct Observation Therapy Strategy (DOTS) in Nigeria

“…Tubercle bacillus contained in such droplets lives in the air for a short time (about two hours) and, therefore, it is believed that occasional contacts with TB-active persons (infectious individuals) rarely lead to transmission, and that the most secondary cases are the result of prolonged and sustained close contacts with a primary case. The case of a teacher-librarian with active TB who infected the children in her classroom but not the children who visited the library [28,24] supports the assertion of the difference between the casual and the close contacts for there to be a transmission of the disease.…”

Unsuspected Recent Transmission of Tuberculosis among High-Risk Groups: Implications of Universal Tuberculosis Genotyping in Its Detection

“…In addition, delays in diagnosis propagated this ongoing transmission. These delays have been described elsewhere as a major reason for community-based TB outbreaks [20][21][22]. Shelters increasingly contribute to recent TB transmission because of crowding and poor ventilation, as well as risk factors (e.g., illicit drug use and alcohol abuse) among the homeless population [5,23,[24][25][26][27].…”

Estudio epidemiológico de la tuberculosis en el Área Sanitaria de Santiago de Compostela durante los años 1995, 1996, 1997 y 1998

“…Así en grandes concentraciones humanas en lugares cerrados como discotecas, pabellones deportivos (17), bares (17,18), etc., es común una escasa ventilación, poca luz, alto porcentaje de humedad y gran proximidad física de los individuos entre sí, sin olvidarnos de los lugares de acceso a tales lugares. Aún hay otras situaciones, con las mismas características, que pueden estar condicionando nuestra alta incidencia.…”

“…Aún hay otras situaciones, con las mismas características, que pueden estar condicionando nuestra alta incidencia. Son aquellas a donde concurren gentes de cualquier grupo de edad, tales como grandes centros comerciales, iglesias (17,19), escuelas (17), centros de acogida (20), prisiones (21,22), hospitales (23), embarcaciones (11,24), aviones (17,25), etc. Por lo tanto, al no haberse modificado en absoluto las circunstancias, principalmente falta de ventilación y gran proximidad física de los individuos, podrían ser éstas algunas de las causas de que los índices epidemiológicos no desciendan con la rapidez deseada.…”