The number of tuberculosis (TB) cases worldwide increased from 6.5 million new cases in 1990 to 8.8 million in 2005. Experts attribute the rise to the increasing number of HIV-infected individuals, whose compromised immune systems make them up to 50 percent more likely to develop TB than individuals without HIV.
"HIV is driving the TB epidemic in general," says Mario Raviglione, director of the World Health Organization's Stop TB Department. The susceptibility of HIV-positive individuals to TB depends on the degree to which the virus has compromised their immune systems, Raviglione explains. Experts describe HIV as "telescoping" the TB epidemic because TB develops more often and quicker in HIV-infected individuals than non-infected people.
Once known as consumption because it caused its victims to waste away, TB is among the oldest and most lethal of human afflictions. Dubbed the "captain of all these men of death" by 17th-century English writer John Bunyan, TB at its peak killed one in every four people in the United States.
TB killed more than 1.5 million people in 2005, the vast majority in developing countries. Overall, one-third of the world's population is infected with TB, but mainly in a latent form. Among people who are not HIV positive, only 5-10 percent of those infected with TB will develop the disease.
While generally considered a lung disease, TB also can affect other body parts, including the central nervous system. TB is curable, but confirming diagnoses is difficult, and the drug regimen is intensive, often taking more than six months. Without treatment, half of those who develop the disease die from it.
An estimated one-third of the 40 million people living with HIV/AIDS are co-infected with TB. "HIV and TB form a lethal combination, each speeding the other's progress," according to the World Health Organization. In addition, TB is harder to diagnose in HIV-positive people, the disease progresses faster and TB occurs earlier in the course of HIV infection than many other opportunistic infections. Without proper treatment 90 percent of people living with HIV/AIDS die within months of contracting TB.
Also complicating TB treatment is the rise since the 1980s of drug-resistant forms, known as multidrug resistant TB (MDR-TB) and extensively drug resistant TB (XDR-TB). The new strains, Raviglione says, take treatment "almost virtually to the pre-antibiotic era."
While HIV is not fuelling drug-resistant forms per se, Raviglione says the new TB strains are particularly deadly for HIV-positive individuals and HIV helps the virulent strains spread faster in some areas. XDR-TB, considered by some to be untreatable, killed 52 of 53 infected patients in rural South African hospitals in late 2005 and early 2006. While XDR-TB is also increasing in Russia and China, health experts are particularly alarmed about the high HIV rates in Africa.
TB has been on the wane in developing countries for some time making it difficult for advocates to generate funding to fight the disease. The Washington-based Global Health Council estimates TB required global expenditures of $3.5 billion to $4.5 billion in 2007, but only half that amount was available.
The reality of drug-resistant TB was brought home to Americans when infected Atlanta lawyer Andrew Speaker boarded several overseas flights last summer, raising an international ruckus. Speaker was first thought to have XDR-TB, but his diagnosis was later changed to the more treatable MDR-TB. Speaker's controversial flights nonetheless focused U.S. attention on the disease that has been worrying global health experts for years. Both the House and Senate are now considering bills that boost funding for global TB efforts.
Noting the connection between the first U.S. drug-resistant TB scare and the increased funding, Raviglione quips, "We need 10 Mr. Speakers every month."