Towards ending tuberculosis: what gets measured gets done


Two major crises

In 2007, when Dr Margaret Chan took office, WHO estimated that 13.7 million people were living with active tuberculosis, including 9.3 million new cases. TB killed an estimated 1.8 million people that year, making it one of the world’s biggest infectious killers. Tuberculosis control faced two major crises. First, the emergence and then explosive spread of the HIV epidemic was accompanied by sharp increases in TB morbidity and mortality. As immunodeficiency spread, more of the roughly two billion people who harmlessly harbour Mycobacterium tuberculosis as a latent infection developed overt disease. The two epidemics converged to deliver an especially deadly blow, most notably in sub-Saharan Africa.

Estimated TB incidence rates
Global TB report 2016: Map of TB incidence
Source: Global TB report 2016

Second, strains of the bacterium resistant to multiple drugs emerged, making multidrug-resistant tuberculosis, or MDR-TB, a formidable new threat. Second-line drugs were toxic, difficult to administer, in short supply, and at least 100 times more costly. Whereas treatment of drug-susceptible TB took six months, the time needed to treat MDR-TB was 20 months or more. Even with the best treatment and supportive care available, fewer than 50% of patients could be cured. The threat was global. In wealthy countries, drug-resistant strains showed how quickly they could exploit populations made vulnerable by poverty, illness, social marginalization, or lack of access to basic health care. In the US, MDR-TB gained its first foothold in the homeless populations living on the streets and sidewalks of New York City.

Moreover, TB experts were still reeling from the results of an investigation of an especially severe TB outbreak at Tugela Ferry Hospital located in a rural and desperately poor district in South Africa. The results of that investigation, published in 2006, found 221 patients with MDR-TB. Of these, 53 were infected with a strain that was resistant to the two most powerful classes of first-line drugs but also to at least two of the six most powerful classes of second-line drugs. All 53 patients were co-infected with HIV. Working together, WHO and the US Centers for Disease Control and Prevention defined the newly detected form of this disease as “extensively drug-resistant TB”, or XDR-TB.

+The two epidemics converged to deliver an especially deadly blow, most notably in sub-Saharan Africa."

Dr Chan, WHO Director-General

Extensively drug-resistant TB was extreme in every sense. It was extremely lethal. Of the 53 patients with XDR-TB, all but one died, with an average survival time of only 16 days following diagnostic confirmation. While some infections had been acquired in the community, the vast majority of infections moved from person to person in the hospital setting. That made the emergence of XDR-TB extremely alarming, as few hospitals in sub-Saharan Africa were equipped to prevent the spread of infection; many had no reliable supplies of electricity or clean running water.

The news quickly got worse. A retrospective investigation, jointly undertaken by WHO and CDC, of samples stored in an international network of specialized TB laboratories confirmed that XDR-TB had already spread well beyond the African continent. By the end of 2014, XDR-TB had been reported in 105 countries, with the highest incidence in Belarus, Georgia, Latvia and Lithuania.