Tuberculosis & HIV

Tuberculosis & HIV

TB is the most common opportunistic infection for HIV and the leading cause of HIV-related deaths.

Once regarded as a disease of poverty, tuberculosis, which is estimated to have infected one-third of the world’s population, is now seen primarily as a disease of disparities—ethnic, racial, geographic, economic, biological. Most of the nine million new cases of TB that emerge each year occur in just 22 “high-burden” countries, chief among them China and India. Prison populations are especially vulnerable, as are people infected with HIV. TB is, in fact, the most common opportunistic infection for HIV and the leading cause of HIV-related deaths.

TB treatments also interfere with antiretroviral therapies commonly used to treat HIV, reports Zhenhua Yang, associate professor of epidemiology at SPH.

Yang has spent almost two decades studying TB. She’s especially interested in the biology of latent-TB infection, which can reside in people for as long as 30 years before awakening to wreak bodily havoc. Despite decades of research, the biological basis of this phenomenon remains poorly understood. Yang’s research has implications for the development of vaccines to prevent latent-TB infection from reactivation and drugs to eliminate the latent-TB bacillus from infected hosts.

What triggers the reactivation of latent TB? The host-immune system almost certainly has an effect, Yang says. Malnutrition can compromise immunity, as can exposure to other pathogens, such as HIV. A person’s genetic, social, and economic status also contributes. “That’s why my future goal for research is really to integrate host-pathogen, environmental, and societal factors,” she explains.

Yang’s research will inform and enrich the World Health Organization’s “Global Plan to Stop TB,” an ambitious campaign to eliminate the disease by 2015. “The more we do, the more leads we have, and the more new research directions,” Yang says. “Sometimes I get so excited.”


  • One-third of the world’s current population is estimated to be infected with TB bacilli
  • Five to ten percent of people who are infected with TB bacilli become sick or infectious at some time in their life
  • People with HIV and TB infection are much more likely to develop active TB
  • TB is the leading cause of death among HIV-infected individuals
  • Worldwide, TB is the leading killer of women, outranking all other causes of maternal mortality
  • TB disproportionately affects people in resource-poor settings, especially those in Asia and Africa
  • The vast majority of TB deaths are in the developing world
  • Strains of TB resistant to all major anti-TB drugs have emerged