“Responding to drug-resistant tuberculosis is possibly one of the most profound challenges facing global health.”1
The past 20 years have seen the worldwide appearance of multidrug-resistant (MDR) tuberculosis,2, 3, 4, 5 followed by extensively drug-resistant (XDR) tuberculosis,6, 7, 8, 9 and, most recently, strains that are resistant to all antituberculosis drugs.10, 11, 12 MDR tuberculosis is caused by Mycobacterium tuberculosis that is resistant at least to isoniazid and rifampicin, and XDR tuberculosis by mycobacteria resistant to rifampicin and isoniazid, any fluoroquinolone, and one of the three injectable drugs, capreomycin, kanamycin, and amikacin. Drug resistance severely threatens tuberculosis control, since it raises the possibility of a return to an era in which drugs are no longer effective.13
Progress is being made in global control of drug-susceptible tuberculosis, as presented by Lonnröth and colleagues14 in the first report in this Series. In 2008, 5·7 million (61%) of the estimated 9·4 million new and relapsed tuberculosis cases were identified and treated on the basis of the WHO Stop TB Strategy.15 Partly as a result of these efforts, worldwide incidence of tuberculosis has been slowly falling since 2004.15 Data are insufficient to indicate whether incidence of MDR tuberculosis is rising or falling globally. However, the fact that only 7% of the estimated 440 000 (95% CI 390 000–510 000) cases of MDR disease worldwide were reported to WHO in 2008, and of these, only a fifth (1·2% of the total) were treated according to WHO recommended standards, is of major concern.15 These data show the depth of the challenge referred to by Upshur and colleagues1—that countries are confronted by huge political, structural, and economic constraints that have to be overcome to tackle the epidemic of drug-resistant tuberculosis. As a result, although the Millennium Development Goal of a reversal in the incidence of tuberculosis seems to have been achieved in 2004,15 progress in the management of MDR tuberculosis has been poor, and milestones in the Stop TB Partnership's Global Plan to Stop TB 2006–2015, are being missed.16 Unless countries can greatly intensify detection and treatment of drug-resistant cases, the possibility remains that MDR strains could become the dominant form of tuberculosis disease.17, 18
Key messages
- •
An estimated 440 000 cases of multidrug-resistant (MDR) tuberculosis occurred worldwide in 2008 (3·6% of the estimated cases of tuberculosis in that year); most of these cases develop as a result of primary transmission (ie, in people never previously exposed to antituberculosis drugs).
- •
Drug-resistant tuberculosis poses a major threat to existing control programmes since treatment is less effective, more complex, and far more costly than is that for drug-susceptible disease.
- •
Tuberculosis control efforts are complicated by weak programmes with poor access to laboratory diagnosis and effective treatment. Investment in laboratory capacity and staff and the introduction of new rapid diagnostic tests are crucial.
- •
Driving forces behind the epidemic of drug-resistant tuberculosis include poor political commitment and weak health policies, regulation, and enforcement—especially uncontrolled drug availability in the private sector.
- •
Outbreaks of MDR and extensively drug-resistant (XDR) tuberculosis have emphasised the need for effective infection-control measures, which are absent in most high-burden settings.
- •
Nonetheless, some countries have reversed rising epidemics of MDR tuberculosis with wise use of existing technologies, and set an example for others.
- •
That new drugs, presently in the pipeline, are not exposed to the same health-system and programme weaknesses that created MDR and XDR tuberculosis is imperative.
In this Series report on drug-resistant tuberculosis, we will explore the size and causes of the MDR and XDR tuberculosis epidemic, and discuss the possible responses that are needed by policy makers globally and nationally if the challenge of drug-resistant tuberculosis is to be adequately faced.