Scientists tracked 107 patients with extensively drug-resistant TB, also known as XDR-TB in three South African provinces between 2008 and 2012. Despite most patients being treated with about eight TB drugs, 78 died.
More than 40 others were released from hospitals without further monitoring. TB is an infectious bacterial infection that usually affects the lungs and is often spread by coughing and sneezing.
In one case, DNA testing confirmed a discharged patient passed on the deadly strain to his brother; both eventually died without being admitted to a hospital.
"These patients can survive for months or even years and are contributing to the community-based spread of XDR-TB," said Keertan Dheda of the University of Cape Town in South Africa, who led the study.
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The research was published online today in the journal, Lancet. Dheda described the situation as alarming and called for modern sanatoriums to be built so patients could be treated away from society.
South Africa has the world's highest number of patients with XDR-TB and health officials warn other drug-resistant forms of the disease are spreading at an increasing rate, most notably in eastern and central Europe, China, India and Africa.
Globally, experts estimate only about one in five people with drug-resistant TB is diagnosed or treated.