Abstract
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Tuberculosis
is a major cause of premature mortality. Communities in Southern Africa are
disproportionately affected. A growing body of evidence suggests that recent
transmission within households can explain only a limited proportion of
tuberculosis disease. However, our understanding of where transmission
between households occurs is limited. I undertook a systematic review and
meta-analysis of molecular epidemiology studies that described rates of
strain discordance in co-prevalent cases of tuberculosis resident in the same
household. I also conducted a tuberculin school survey in 6-8 year old
children in a rural community in Northern KwaZulu-Natal. These children were
all registered in a household surveillance programme operated by the Africa
Centre for Population Health. I found that, across a range of both high and
low burden countries, co-prevalent cases of tuberculosis in the same
household often have different strains of Mycobacterium tuberculosis. These
molecular epidemiological data suggest, at least in some settings, that
recent transmission within households may explain a modest proportion of
tuberculosis disease. I estimated the annual risk of tuberculous infection to
be approximately two percent in the community around the Africa Centre. I found
weak evidence that exposure to HIV positive adults in the household was
associated with Mycobacterium tuberculosis infection in children. I found no
strong evidence associating use of specific indoor public spaces with
Mycobacterium tuberculosis infection. Transmission between households is
likely an important determinant of tuberculosis disease. Further research
locating Mycobacterium tuberculosis transmission might enable TB control
interventions to be better targeted.
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