People in South Africa are suffering from the deadliest type of tuberculosis (TB), and researchers say treatment failure is not to blame.

Extensively Drug-Resistant Tuberculosis (XDR-TB)

XDR-TB is a rare but extremely fatal type of tuberculosis that is resistant to at least four of the core anti-TB drugs.

This disease is so serious that it's unaffected even by two of the most potent tuberculosis drugs — isoniazid and rifampicin — making it a multidrug-resistant tuberculosis (MDR-TB). XDR-TB is also highly resilient to other tuberculosis drug treatments, such as fluoroquinolones and to at least one of the three injectable second-line TB drugs (amikacin, kanamycin, or capreomycin).

Because it's tougher to treat than ordinary tuberculosis, more aggressive XDR-TB treatment options are necessary and require the use of second-line anti-TB drugs, which are more expensive, take longer to come into effect, and have several side effects.

Treatment can last up to two years, and in the end leaves XDR-TB patients with permanent hearing loss, nerve damage, depression, gastrointestinal issues, psychosis, kidney failure, and drug-induced hepatitis.

Still, this doesn't always guarantee survival. Between 50 percent and 80 percent of those who start XDR-TB treatment die.

Worst XDR-TB Outbreak In South Africa

Although XDR-TB is rare, 117 countries worldwide had reported at least one case by the end of 2015, according to the World Health Organization.

According to a press release by the U.S. Centers for Disease Control and Prevention, South Africa is going through a rampant epidemic of XDR-TB, with a tenfold increase in cases between 2002 and 2015. The worst XDR-TB outbreak is seen in the rural mountain regions of the country behind Durban, where human immunodeficiency virus (HIV) is also widespread.

Death Of XDR-TB Patients With HIV

In 2006, at the 16th International Conference on AIDS, Emory University's Neel R. Gandhi, M.D. reported that 52 out of 53 XDR-TB patients, who were also infected with HIV, had died in a rural hospital in South Africa.

At first, researchers believed that the patients developed XDR-TB because of treatment failure, which may involve drug resistance, not taking the right medications, or not having taken any at all. But after learning that many of the patients had never undergone TB treatment, they began looking closer at person-to-person transmission of the virulent disease.

New Evidence On Direct Transmission Of XDR-TB

Published recently in the New England Journal of Medicine, a new study from South Africa, led by Dr. Gandhi and Dr. Sarita Shah CDC's Division of Global HIV & TB, looked at 404 XDR-TB patients in KwaZulu-Natal, South Africa.

With the use of a combination of advanced strategies — genotyping methods with social network and epidemiologic analysis — researchers have found that majority of cases (69 percent) in high HIV- and high TB-burden areas happened due to close contact with an infected person — including coughing, kissing, or sharing food and drink — and not because of inadequate treatment. The study also cited hospitals and community settings, such as households and workplaces, as infection-prone areas.

"These findings provide insight as to why this epidemic continues despite interventions to improve TB treatment over the past decade. Public health and research efforts must focus more intensely on identifying and implementing additional or new interventions that halt transmission in hospitals and community settings." Dr. Gandhi explained.

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