Cover Image
close this bookFact sheet No 104: Tuberculosis - Revised April 2000 (WHO, 2000, 3 p.)
View the document(introduction...)
View the documentInfection and Transmission
View the documentGlobal and Regional Incidence
View the documentFactors Contributing to the Rise in TB
View the documentEffective TB Control

Factors Contributing to the Rise in TB

HIV is accelerating the spread of TB

HIV and TB form a lethal combination, each speeding the other's progress. HIV weakens the immune system. Someone who is HIV-positive and infected with TB is many times more likely to become sick with TB than someone infected with TB who is HIV-negative. TB is a leading cause of death among people who are HIV-positive. It accounts for about 15% of AIDS deaths worldwide. In Africa, HIV is the single most important factor determining the increased incidence of TB in the last ten years.

Poorly managed TB programmes are threatening to make TB incurable

Until 50 years ago, there were no drugs to cure TB. Now, strains that are resistant to a single drug have been documented in every country surveyed and, what is more, strains of TB resistant to all major anti-TB drugs have emerged. Drug-resistant TB is caused by inconsistent or partial treatment, when patients do not take all their drugs regularly for the required period because they start to feel better, doctors and health workers prescribe the wrong treatment regimens or the drug supply is unreliable. A particularly dangerous form of drug-resistant TB is multidrug-resistant TB (MDR-TB), which is defined as the disease due to TB bacilli resistant to at least isoniazid and rifampicin---the two most powerful anti-TB drugs. MDR-TB is rising at alarming rates in some countries, especially in the former Soviet Union, and threatens global TB control efforts.

From a public health perspective, poorly supervised or incomplete treatment of TB is worse than no treatment at all. When people fail to complete standard treatment regimens, or are given the wrong treatment regimen, they may remain infectious. The bacilli in their lungs may develop resistance to anti-TB drugs. People they infect will have the same drug-resistant strain. While drug-resistant TB is treatable, it requires extensive chemotherapy (up to two years of treatment) that is often prohibitively expensive (often more than 100 times more expensive than treatment of drug-susceptible TB), and is also more toxic to patients.

WHO and its international partners are have formed the DOTS-Plus Working Group, which is attempting to determine the best possible strategy to manage MDR-TB. One of the goals of DOTS-Plus is to increase access to expensive second-line anti-TB drugs for WHO-approved TB control programmes in low and middle income countries.

Movement of people is helping the spread of TB

Global trade and the number of people travelling in aeroplanes have increased dramatically over the last forty years. In many industrialized countries, at least one-half of TB cases are among foreign-born people. In the US, nearly 40% of TB cases are among foreign-born people.

The number of refugees and displaced people in the world is also increasing. Untreated TB spreads quickly in crowded refugee camps and shelters. It is difficult to treat mobile populations, as treatment takes at least six months. As many as 50 percent of the world's refugees may be infected with TB. As they move, they may spread TB.

Other displaced people such as homeless people in industrialized countries are at risk. In 1995, approximately 30 percent of San Francisco's homeless population and 25 percent of London's homeless were reported to be infected with TB. These figures compare to overall prevalences of 7 percent in the United States and 13 percent in the United Kingdom. The prevalence of infection in prisons can be even higher.