TB, or tuberculosis, is a deadly infectious disease caused by strains of the microorganism mycobacteria, which causes no observable symptoms in 90 percent of individuals, with the remaining 10 percent going on to develop TB. Tuberculosis is the leading infectious killer of people with weakened immune systems due to HIV infection, accounting for an estimated 23 percent of AIDS-related deaths in 2008, according to the World Health Organization.
T Helper Cells
The activity of a group of white blood cells known as T helper cells is crucial for the immune system to combat the TB pathogen in otherwise healthy individuals. The HIV virus specifically targets T helper cells, greatly reducing their concentration in the blood, leaving individuals more vulnerable to the TB pathogen, according to an August 2008 article published in "Lancet Infectious Diseases."
Risk of TB
The greatest single risk factor for developing or suffering a recurrence of TB is HIV. Over a lifetime, HIV-negative patients who have previously had TB have a 5 to 10 percent risk of suffering a recurrence of the disease, which is increased to 30 percent or more in HIV-positive individuals, according to a May 2003 article published in "Archives of Internal Medicine."
TB Progression
Infectious lesions caused by TB are predominately localized to the lungs and respiratory tract in HIV-negative patients, but far more likely to spread to other organs such as the liver and spleen in HIV-positive individuals, leading to a more severe prognosis, according to an April 2005 article published in the "Indian Journal of Medical Research."
HIV Progression
At sites of TB infection in the lungs, replication of the HIV virus is increased, leading to a more rapid progression of HIV and increasing the severity of the prognosis, according to a September 2001 article published in the "Journal of Acquired Immune Deficiency Syndromes."
Treatment Problems
The type of highly active retroviral therapy commonly used to treat patients with HIV frequently induces side effects in patients taking extended courses of antibiotics specifically used to treat TB. In most cases, doctors decide the TB medication takes precedence over the HIV treatment due to the rapid progression and poor prognosis of TB, particularly in HIV infected individuals, according to an April 2005 article published in the "Indian Journal of Medical Research."
References
- World Health Organization: Tuberculosis and HIV
- "Archives of Internal Medicine"; The Growing Burden of Tuberculosis: Global Trends and Interactions with the HIV Epidemic; E. Corbett, et al.; May 2003
- "Lancet Infectious Diseases"; Paediatric Tuberculosis; S. Newton, et al.; August 2008
- "Indian Journal of Medical Research"; HIV-TB co-infection: Epidemiology, Diagnosis & Management; S. Sharma; April 2005
- "Journal of Acquired Immune Deficiency Syndromes"; Increased Replication of HIV-1 at Sites of Mycobacterium Tuberculosis Infection: Potential Mechanisms of Viral Activation; S. Toossi; September 2001
