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Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Speaker Abstracts
20
Novel Approaches to the Aerobiology of Tuberculosis Transmission
Robin Wood
.
Desmond Tutu HIV Centre, IDM, Faculty of Health Sciences, University of Cape Town, Cape
Town, South Africa.
South Africa has the highest tuberculosis notification and death rate of any country worldwide.
The city of Cape Town alone has more TB notifications annually than USA, Canada, UK and
France combined. TB transmission rates have remained at levels recorded in industrial cities of
Europe and North America a century ago. Transmission is determined by the combination of the
prevalence of infectious TB in the community, the social and environmental factors enabling air
exchange from infective individuals, and the concentration of TB bacilli in the exhaled air of
infectious.
Our knowledge of the airborne nature of respiratory disease transmission owes much to the
pioneering experiments of Wells and Riley over half a century ago. However,
these in vivo animal studies may have considerably underestimated the potential infectivity of
TB cases.
In order to better characterize the factors driving TB transmission in a Cape Township
social environments conducive for potential TB transmission in Cape Town were identified using
a combination of social mixing studies and the use of carbon dioxide as a natural tracer gas as a
proxy for TB exposure. The volumes of air exchanged between individuals were calculated
during different activities and seasons.
The potential infectivity of TB patients was explored by sampling devices installed in a
Respiratory Aerosol Sampling Chamber (RASC) that enabled representative sampling and
isolation of airborne particles and organic matter from TB patients. Preliminary results from the
first 10 TB patients showed the presence of airborne bacilli on scanning electron microscopy, the
presence of culturable TB organisms and high levels of TB DNA in the expired air of these
patients.