Skip to Main Content

There’s more bad news on the antibiotic resistance front.

A new study reveals that strains of tuberculosis that evade most of the drugs typically used to treat the bacterial infection have been spreading in South Africa, which already has a high rate of tuberculosis infection.

Extensively drug-resistant tuberculosis — known by the short form XDR TB — is highly concerning to health authorities because of the way tuberculosis spreads. Infected people expel bacteria from their lungs when they cough, sneeze, even speak. The bacteria can float for hours under the right conditions, infecting people who breathe them in.


About half of South Africa’s cases were in KwaZulu-Natal, a coastal province that includes the city of Durban.

The research, published Wednesday in the New England Journal of Medicine, does not suggest that extensively drug-resistant tuberculosis is spreading rapidly. But it does suggest that, of those tuberculosis cases in South Africa, far more are the result of transmission from person to person than previously known, rather than the result of improper medical treatment. The scientists — from the US and South Africa — found that in about 400 people studied, most had become infected by contracting the bacteria from someone else.


“We all know that tuberculosis is something that spreads between people, but it just hasn’t been as big a focus with XDR and MDR [multi-drug resistant] TB because there’ve been so many treatment failures that have caused [new] cases,” said Dr. Michael Gardam, who runs a TB clinic at Toronto’s University Health Network. Gardam was not involved in the study.

“But this case is showing this can spread quite nicely between people, and that’s even more terrifying in a way. Because you could just be in the wrong place at the wrong time.”

Extensively drug-resistant tuberculosis is still rare in the US, with fewer than five cases a year in the country, said Dr. Peter Cegielski, team lead for TB at the Centers for Disease Control and Prevention.

Several of the scientists responsible for the study work in Cegielski’s department. Cegielski and his colleague, Dr. Sarita Shah, reported the first cases of extensively drug-resistant tuberculosis TB in 2005, and Shah is the lead author on the new study.

Extensively drug-resistant TB is both difficult and costly to treat and treatment is often not successful. The fatality rate is between 50 percent and 80 percent, the study noted. The combination of XDR TB and HIV is particularly deadly.

Even though XDR TB is highly concerning to health authorities, TB is not as contagious as some other airborne pathogens, things like measles or chickenpox. Still, it is a major global threat, and one of the top 10 causes of death worldwide, according to the World Health Organization.

Tuberculosis is a bacterial infection that most often attacks the lungs. Most infections are latent; the bacteria are harbored in the body but don’t cause disease. The WHO estimates that about a third of the world’s population has latent TB.

People with latent tuberculosis have a 1 in 10 risk of developing active disease at some point. Symptoms of active disease are initially mild and include coughing, fever, night sweats, and weight loss. But untreated tuberculosis can be fatal.

The WHO estimates that in 2015, 10.4 million people were sickened by tuberculosis and 1.8 million died.

In this study, researchers from the CDC and a number of universities investigated 404 XDR TB patients to see if they were infected by others or had developed the resistance on their own. The scientists searched medical records and studied the genetic sequences of samples of bacteria collected from the patients. Closely related bacteria indicate transmission, not acquired resistance.

Inadequate treatment accounted for at most 31 percent of the cases, they reported. Some of the XDR TB transmission occurred in hospitals — a known risk — but some occurred in the community, they noted.

“It’s not a surprise that there’s so much transmission of tuberculosis, even highly drug-resistant tuberculosis going on in institutions. But I think it’s very important that they were able to quantify it using these state of the art scientific methods,” Cegielski said of the study.

He said a lot of work is underway to develop better methods of treating XDR TB cases and preventing transmission of this infection in hospitals. The findings, he noted, suggest “we need to redouble our efforts.”

That is true not just about XDR TB but tuberculosis in general, said Dr. Philip Lederer, an infectious diseases specialist at Massachusetts General Hospital and Harvard Medical School.

“This study points to the critical importance of transmission and the critical need for more funding and resources at all levels, from WHO to national TB programs, to research, to advocacy,” Lederer said. “It’s very neglected by the global health community.”

  • I am australian & closely involved with a family in indonesian west timor whose 20 yr old son has been diagnosed.with tb. I am confident the care on offer here in the provincial capital of .Kupang is equal to that available elsewhere in the country but i would like to know if who has any stats for the disease in these parts.

  • Dear Helen,
    Thank you for this important and informative article! I’m a passionate TB survivor and activist working with TB Proof, a non-profit organization in South Africa. I’d like to discuss a few concerns with you and also 5 ways in which anyone, anywhere can help.
    Though the study mentioned is based in South Africa, the extent of this problem is far beyond South Africa – by the end of 2015, extensively drug-resistant TB (XDRTB) had been reported by 117 WHO Member States. Most of the XDRTB cases in 2015 were notified by India (2130), Ukraine (1206), the Russian Federation (1205)
    and South Africa (719). The six countries that stood out as having the largest
    number of TB incident cases (these numbers include all forms of TB) in 2015 were (in descending
    order) India, Indonesia, China, Nigeria, Pakistan and South
    Africa (combined, 60% of the global total). Of these, China,
    India and Indonesia alone accounted for 45% of global
    cases in 2015.
    What makes TB more dangerous than other airborne illnesses mentioned is its chronicity, habit of passing undetected and challenging treatments, hence the severe morbidity and mortality that far exceeds that of chicken pox or measles. While you can easily see chicken pox, you can’t see TB – there needs to be a cultural shift towards people wearing masks (correctly) whenever they have a respiratory illness, whatever the diagnosis.
    An important finding in this article is that even people who have never had TB before can get extremely drug-resistant TB from those who have this infection and are in the infectious stage.
    People from countries with low TB rates also need to respond to this global emergency. Why? People travel and relocate, and if you breathe in TB and don’t get ill in the year or two following exposure, it can still lie dormant in your lungs for years, popping up if your immune system is suppressed due to illnesses like diabetes or HIV, or immune-suppressant therapies. You (or your doctor) might not consider that you may have TB and it could take a long time to be diagnosed, during which time the infection could pass to others. TB is not only a problem in poor areas and even healthy people can get TB. The TB vaccination given to some babies at birth does not prevent you from getting TB, it only helps prevent complicated forms of TB in children.
    Here are 5 ways in which people everywhere can respond to this global emergency: 1: Know the correct facts (WHO and CDC are resources) so we avoid stigma, which is very harmful to our efforts. 2: Drive a cultural shift to wear a mask (correctly) whenever you have any kind of respiratory illness, even if it’s just a common cold. 3: Support people who get TB – this illness causes much loss and isolation. 4. Identify and support organizations working to end TB as they are often struggling to get funding and 5: Drive campaigns (even if it’s as simple as a social media post or forwarding information from an article or campaign) that are holding governments accountable for putting adequate TB prevention measures in place.
    I’d like to thank partners and staff involved in implementing the NiX-TB trial in South Africa – the first study to test an all-oral drug regimen that has the potential to shorten, simplify, and improve treatment for XDR-TB.
    Thanks again Helen, you are welcome to contact me at any time. Chanèl.

    • Thanks Chanel. Just a minor comment, as per latest WHO Global TB Report 2016, burden of TB in terms of notifications in 2015 in absolute numbers in K are in this order;
      1. India 1741
      2. China 804
      3. Pakistan 332
      4. Indonesia 331
      5. South Africa 295
      6. Philippines 287
      7. Bangladesh 209
      8. Myanmar 141
      9. Ethiopia 138
      10. Russian Fed 131

      Only 2 out of these South Africa and Indonesia pop up in top 10 List according to ranking by TB incidence rates per 100K population. Often these subtle observations don’t get reflected well.

      Also the recent NEJM paper on XDR-TB transmission guide us to focus further on infection control and in particular using right N95 masks for XDR-TB patients.

      Let the entire TB scientific community put their one cent effort in out battle against the resilient Mycobacterium tuberculosis. Thanks.

    • Thanks for pointing that out, Shree, I’ve also taken my stats from WHO, but I have managed to find the reason for this error:
      The WHO Global TB Report 2016 states the following: ‘Six countries accounted for 60% of the NEW cases: India,
      Indonesia, China, Nigeria, Pakistan and South Africa’.
      The WHO’s online media centre tuberculosis fact sheet ( states this as ‘Six countries account for 60% of the total, with India leading the count, followed by Indonesia, China, Nigeria, Pakistan and South Africa’; they have omitted the word ‘new’ from this sentence, which is a mistake.
      It makes a lot of sense to look at burden in terms of notification rates and not just in terms of incidence rates, thanks for commenting on that.
      Myanmar and Philippines are with South Africa and Indonesia in the top 10 countries for TB incidence rates per 100K population.
      For anyone who would like to look at the stats, the WHO Global TB Report 2016 is available for download on the WHO website and the stats mentioned here are in Annex 2.
      Great discussion!

Comments are closed.