Tuberculosis (TB) is not only completely treatable, it is curable and controllable, and has been so for decades. So it is appalling that the disease is currently flaring up around the world in an epidemic of co-infection with HIV, which is also associated with a frightening increase in strains of TB that are resistant to existing drugs.

This week, the 38th Union World Conference on Lung Health convenes in Cape Town, South Africa. The main themes of the meeting will be the challenges of HIV–TB co-infection and multiple-drug resistance in TB.

Researchers, doctors and health-care workers need to do far more to respond to the scale of the problem that TB and co-infection with HIV presents.

The importance of co-infection has been emerging steadily, especially in Africa, since the early days of the AIDS pandemic. TB is now the most common opportunistic infection in HIV-positive patients starting antiretroviral therapy. Such co-infection presents particularly troubling complications for treatment: there are overlapping drug toxicities and the risk of a life-threatening inflammatory syndrome if infection status is unknown and treatment administered incorrectly.

The South African city of Tugela Ferry presents a startling example of how an HIV–TB epidemic could play out. The incidence of TB there is very high, and of some 400 multidrug-resistant cases identified since 2006, more than half were classified as extensively drug resistant, meaning that they are resistant to second-line as well as first-line drug treatments. Most of the resistant infections occur in individuals co-infected with HIV. Efforts to manage both diseases in patients may itself encourage the emergence of drug-resistant strains.

Activists and health-care workers have often sought to blame the South African government for its lax response to this crisis. But it has also been aggravated by an unfortunate historical divide in the worlds of research and health care between those addressing TB and those tackling AIDS (see Nature 446, 109–110; doi:10.1038/446109b 2007). Researchers, doctors, health-care workers and the entities that support them need to do far more to respond to the scale of the problem that TB presents, and its interconnectedness with HIV. Priorities outlined in 2004 by the World Health Organization for HIV/TB research have not been implemented adequately, according to a report released by the Forum for Collaborative HIV Research last week.

Large parts of sub-Saharan Africa are becoming subsumed by co-infection. And although the rate of infection has dropped elsewhere, many European and Asian nations still face large numbers of patients with active TB infections. A report from the US Centers for Disease Control and Prevention last month showed that the phenomenon may present a threat in the United States as well (Morbid. Mortal. Wkly Rep. 56, 1103–1106; 2007). One-third of TB patients there didn't know their HIV status, despite official policy that routine testing be performed on everyone with TB. And 9% of those with TB were also HIV positive, according to the report.

The global co-infection epidemic is all the more troubling because it was potentially avoidable with better use of existing drugs. The rising incidence of drug-resistant TB is now forcing agencies in Africa and around the world to react to the scale of the problem. The list of needs is a familiar one: better delivery of existing care approaches, development of more useful diagnostics, and community-based care. But a bigger mental shift is needed in recognizing the size of the problem and its interconnectedness with the AIDS pandemic.