Tuberculosis

Tuberculosis (TB) is a disease caused by a bacterium called Mycobacterium tuberculosis. Nearly one-third of the world's population is infected with TB bacilli. Those with a healthy immune system have a 5 to 10% lifetime risk of developing active disease. Someone with HIV who is exposed to TB has a 10% annual risk of developing active disease. TB is a preventable and treatable disease, but only if it is diagnosed and there is access to treatment.

In 2007 there were 9.3 million incident cases of TB; an estimated 1.4 million (14%) were diagnosed in persons with HIV. Overall, 55% of incident cases occur in Asia and about 31% in Africa; however, 79% of people dually infected live in Africa and 11% live in Southeast Asia. Worldwide prevalence of TB is estimated around 13.7 million and it causes more deaths annually than any other infectious disease. In 2007, TB was thought to be the cause of death in 456,000 HIV-positive individuals and 1.3 million HIV-negative individuals. Of the estimated 2 million deaths from HIV that occurred that year, roughly one-third were attributed to active TB infection.1 

In countries with a generalised HIV epidemic, HIV-infected people are about 20 times more likely to develop active TB disease than are HIV-negative counterparts. In countries where HIV prevalence is lower, the risk of developing active disease is somewhere between 26 and 37 times higher in those who are HIV-positive. Multidrug-resistant tuberculosis (MDR-TB) incidence was estimated at a half million cases in the same year. Up to 96% of incident cases of MDR-TB are not diagnosed and treated in time.

According to WHO, a majority of HIV-positive individuals with TB do not know their HIV status, and of those that do, a majority do not have access to antiretroviral therapy. When treatment for susceptible TB is available, it is as effective in HIV-infected individuals as it is in those who are HIV-negative, although occasionally a longer treatment duration may be required.2 

In developed countries, all forms of TB are considered AIDS-defining illnesses. The WHO staging system used in most developing countries considers only extrapulmonary TB to be AIDS defining.

The 2009 guidance from the WHO recommends antiretroviral treatment with an efavirenz-based regimen for everyone with TB regardless of CD4 count, with antiretroviral therapy to be initiated soon after TB treatment is started.

 

References

  1. World Health Organization Global Tuberculosis Control 2009. World Health Organization, Genva [available online at www.who.int/tb/publications/global_report/en/ accessed 21 november 2009], 2009
  2. American Thoracic Society, CDC, and Infectious Diseases Society of America. Treatment of Tuberculosis MMWR 52 (RR11): 1-77, 2003