| Why should we be concerned about TB and HIV co-infection?
The World Health Organization (WHO) estimates that 11.4 million people worldwide are infected with both mycobacterium tuberculosis and HIV.
HIV, AIDS and TB are so closely connected that the term “co-epidemic” or “dual epidemic” is often used to describe their relationship. HIV and TB form a lethal combination, each speeding the other's progression.
What are the interlinkages?
HIV weakens the immune system. Someone who is HIV positive and infected with TB bacilli is at much greater risk to develop active TB disease than someone infected with TB bacilli who is HIV negative.
How serious is TB and HIV co-infection to the public health system?
TB and HIV co-infection is a very serious public health problem all over the world, but especially in areas with a high burden of TB and HIV such as in sub-Saharan Africa. According to UNAIDS estimates for the 2008, around 33 million people were living with HIV and AIDS. In 2007, there were am estimated 1.37 million new cases of tuberculosis among HIV-infected people and 456 000 deaths. TB is the leading cause of death among people living with HIV, responsible for around 10–15 % of all HIV/AIDS related deaths all over the world. In Africa, HIV is the single most important factor contributing to the increased incidence of TB in the past decade.
What are the TB risks for people living with HIV and AIDS?
A person can have latent TB infection for years and usually only 10 percent of people infected with TB develop TB disease. But if that person’s immune system gets weak due to HIV, the latent TB infection can quickly turn into active TB disease. Also, if a person who has a weak immune system spends time with someone with active TB disease, there is a greater chance that the exposure can lead to infection and quickly develop active TB disease. Besides this, TB disease also reduces the CD4 count levels and thus can lead to weakening of the immune system.
What is the importance of testing for TB?
All PLHIV in high TB prevalence settings should be screened by their medical provider for exposure to TB during each visit. If exposure to TB seems likely, based on a series of yes/no questions, the person should be tested to find out if they have latent TB infection. If they have latent TB infection, they need to make sure to rule out active TB disease and get treatment as soon as possible to prevent them from developing active TB disease. If they have active TB disease, they must take medicine to cure the disease. Active TB disease can be prevented and cured, even in people with HIV infection.
What are the difficulties in diagnosing TB in HIV infected people?
Diagnosing TB in people with HIV infection is often difficult. PLHIV may experience symptoms similar to those of TB and when tested for exposure may not react to the standard TB skin test because their immune system does not work properly. Chest x-rays, sputum tests, and physical exams may also fail to show evidence of M. tuberculosis infection in people with HIV, particularly among people with severe immune impairment.
What are MDR-TB and XDR-TB?
MDR-TB or multiple drug resistant are TB bacteria that are resistant to Rifampin (R) and Isoniazid (H), two of the most potent TB drugs currently available.
XDR-TB or extensively drug resistant TB is TB bacteria that have resistance to Rifampin, Isoniazid, as well as any quinolone (a drug class) as well as two of the three second-line injectable drugs,(kanamycin, capreomycin, or amikacin).
Because MDR and XDR need to be treated for a longer period, and because their treatment has greater side effects, it is difficult to treat these forms of TB. However, if diagnosed and treated appropriately, these conditions can be successfully cured even among PLHIV.
References:
1. WHO: Fact Sheet - TB/HIV Co-infection and Drug-Resistant TB, 2006
2. WHO: TB Fact sheet N°104 - Tuberculosis, March 2007
3. SATAMO: factsheet 2008
4. Health Canada: Tuberculosis Fact Sheet – TB and HIV Infection
5. CDC: Questions and Answers About TB, 2005
6. http://www.who.int/mediacentre/factsheets/fs104/en/
7.http://www.who.int/3by5/en/TBfactsheet.pdfdata.unaids.org/pub/factsheet/2006/tb_hiv_qa.pdf
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