Abstract
BackgroundTuberculosis remains a major public health problem in poverty-stricken areas of the world. Communal gathering places account for the majority of TB transmission in high burden settings.ObjectiveTo investigate the social behaviour patterns of individuals who have developed TB disease and adolescents at risk of infection. To develop a cheap and effective method to locate transmission hot spots in high burden communities.DesignPortable, combined CO2/GIS monitors and location diaries were given to individuals from a South African township. The three groups: newly diagnosed TB patients, recently treated TB patients and adolescents recorded their activities over a median of two days. Rebreathed air volumes (RAVs) at all GIS locations were calculated from CO2 levels using the Rudnick-Milton variant of the Wells-Riley TB transmission model. Hot spot analysis was performed to determine the communal buildings which correspond to spatially clustered high RAVs.ResultsAnalysis of diaries found that the adolescent group spent greater time in congregate settings compared with the other two groups driven by time spent in school/work (new TB: 1%, recent TB: 8%, and adolescents: 23%). Adolescents also changed their location more frequently (9.0, 6.0, 14.3 changes per day; p < 0.001). The RAVs reflected this divergence between the groups (44, 40, 127 l; p < 0.001). Communal buildings associated with high RAVs were found to be a clinic, two schools and a library. Hot spot analysis revealed the most intense clustering of high RAVs at a community school.ConclusionOur study demonstrates a new methodology to uncover TB transmission hot spots using a technique that avoids the need to pre-select locations. Investigation of a South African township highlighted the high risk potential of schools and high risk social behaviour of adolescents. Consequently the targeting of transmission reduction strategies to schools may prove highly efficacious in high burden settings.
Highlights
Global TB prevalence is declining at a rate of 1.5% per annum (WHO, 2014)
Our study investigated a community with frequent transmission events as demonstrated by an undiagnosed prevalence rate N 2000 per 100,000 (Wood et al, 2007) and a latent TB infection rate that reaches 88.0% by age 31–35 (Wood et al, 2010)
Differences were significant with respect to the mean number of cohabitees for the new TB, previous TB and adolescent groups (1.5, 2.8, 3.7 respectively; p = 0.004) and mean number of those sharing a room to sleep (0.4, 1.2, 1.4 respectively; p = 0.024)
Summary
Global TB prevalence is declining at a rate of 1.5% per annum (WHO, 2014). there are still an estimated 9.6 million new TB case notifications each year (WHO, 2014). In South Africa the rates of TB infection are similar to those of 100 years ago driven by a force of infection estimated to be 4–8% (Wood et al, 2011). Hot spot analysis was performed to determine the communal buildings which correspond to spatially clustered high RAVs. Results: Analysis of diaries found that the adolescent group spent greater time in congregate settings compared with the other two groups driven by time spent in school/work (new TB: 1%, recent TB: 8%, and adolescents: 23%). Results: Analysis of diaries found that the adolescent group spent greater time in congregate settings compared with the other two groups driven by time spent in school/work (new TB: 1%, recent TB: 8%, and adolescents: 23%) Adolescents changed their location more frequently (9.0, 6.0, 14.3 changes per day; p b 0.001). Hot spot analysis revealed the most intense clustering of high RAVs at a community school
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