Date of Award

January 2014

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Albert I. Ko

Abstract

Tuberculosis (TB) incidence in Brazilian penitentiaries is extremely high as prisons provide ideal conditions for airborne contagion by congregating infectious and susceptible individuals for extended periods of time. We aimed to determine the effects of architectural, environmental, and ventilation factors that impact TB transmission probabilities across prison cells in three penitentiaries of Mato Grosso do Sul, Brazil. We collected descriptive data on cell architectural characteristics and estimated ventilation rates using steady-state exhaled carbon dioxide levels. A hierarchical linear, multivariable model was used to examine cell level architectural and environmental factors affecting absolute ventilation. We then estimated the probability of TB infection for inmates sharing a cell with an infectious case, using a modified Wells-Riley equation for airborne infection. We projected the impact of improving ventilation to international standards for infection control settings and reducing the time to TB diagnosis by 25%. The three prisons contained 141 prison cells with a range of occupancy from 2 - 30 inmates per cell (p < 0.001). In multivariable analysis, absolute ventilation was positively associated with floor area, ceiling height, opening area, opening area to floor area ratio, opening to volume ratio, and area of courtyard space, and negatively associated with number of cells per courtyard. The projected median risk of TB infection for a person sharing a cell with an infectious case for four months ranged from 53.3% - 69.6% between the three prisons (p < 0.001). Improving ventilation to a minimum of 12 air changes per hour or decreasing time-to-diagnosis decreased transmission by 8.3% and 9.1%, respectively. In contrast, improving per person ventilation rates to World Health Organization recommended levels for health-care settings decreased TB transmission probability by 36.1% and 60.3%. Environmental conditions of Brazilian prisons are highly conducive to the spread of TB. Improving ventilation in prisons may decrease TB transmission risk and, combined with other strategies, may enhance TB control efforts.

Comments

This is an Open Access Thesis.

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