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24 Mar 2016

Risk of active TB developing after being infected much higher than first thought

New estimates for the risk of active tuberculosis (TB) developing in people who are infected with the disease are up to six times higher than previously reported by the World Health Organization.

Published in the journal Chest, the research, led by Dr James Trauer from Royal Melbourne Hospital’s Victorian Tuberculosis Program at the Doherty Institute, found the risk of developing TB after close contact with someone with the disease could be up to 18 per cent – the World Health Organization estimates the risk at five to 10 per cent.

“Approximately a third of the world’s population is infected with TB, and close contacts are at a particularly high risk of being infected,” Dr Trauer said.

“In this study, we found the risk of developing TB within five years of being exposed was 11 to 18 per cent. The risk was particularly high in children under five and in the first five months following infection.”

Using notification data from the Victorian Tuberculosis Program a group of close contacts of TB cases were identified who were known to have been infected with TB as a result of their exposure.

The data was then analysed to determine the risk of progression to active disease.

“The risk of developing active TB is likely to be much higher in developing countries, as well as in populations with a high prevalence of co-morbidities such as HIV and malnutrition, so these estimates could be even higher in those settings,” Dr Trauer said.

He explained the results highlighted the importance of interventions, especially preventive treatment, during the period shortly after infection.

Co-author and Medical Director of the Victorian Tuberculosis Program, Associate Professor Justin Denholm said the result would be likely to change some international policies around post-exposure management of TB.

“While international policies have previously recommended preventive treatment for young children exposed to TB, practice has sometimes been patchy and older contacts have often been overlooked,” Associate Professor Denholm said.

“This research should encourage programs around the world to strengthen their approach to finding those at risk and preventing disease, which is critical as we work towards global elimination of TB.”

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