March 2012

HIV and 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 bacilli is about 21-34 times more likely to develop TB disease compared with those who are HIV-negative.
  • In 2010, there were 1.1 million new TB cases among people living with HIV.
  • TB is a leading cause of death among people who are HIV-positive.
  • In Africa, HIV is the single most important factor contributing to the increase in the incidence of TB since 1990.

Drug-resistant TB

  • Until 70 years ago, there were no medicines to cure TB.
  • No new anti-TB drugs have been developed in nearly 50 years.
  • Strains that are resistant to at least one drug have been documented in every country surveyed.
  • Strains of TB resistant to all major anti-TB drugs have now emerged.
  • Drug-resistant TB is the result of inadequate treatment and is, thus, man-made. It is caused by inconsistent or partial treatment, when patients do not take all their medicines regularly (because they start to feel better, doctors and health workers prescribe the wrong treatment regimens, drug supply is unreliable or of poor quality).
  • The vast majority of TB patients do not have access to laboratory tests to detect drug resistance.
  • A particularly dangerous form of drug-resistant TB is multidrug-resistant TB (MDR-TB), when TB bacilli are resistant to at least isoniazid and rifampicin, the two most powerful anti-TB drugs.
  • MDR-TB is treatable, but requires extensive chemotherapy (up to two years of treatment) with second-line anti-TB drugs.
  • Second-line drugs are more costly than first-line drugs, and cause adverse drug reactions that are more severe, though manageable.
  • Extensively drug-resistant (XDR) TB, particularly in settings where many TB patients are also infected with HIV, confirms the need for urgent action to strengthen basic TB control.
  • XDR-TB is defined as MDR-TB that is, in addition, resistant to the two most powerful second-line anti-TB drugs, any fluoroquinolone and any second-line anti-TB injectable.
  • 47 countries are using Xpert MTB/RIF, a rapid molecular test that accurately diagnoses TB and MDR-TB in 100 minutes. The test was endorsed by WHO in December 2010, with 145 countries eligible to purchase the kits at a concessional price.