Almost 50 percent of HIV-infected individuals worldwide will not die from the disease itself but, rather, from tuberculosis, according to the Centers for Disease Control (CDC).

Tuberculosis (TB) is caused by a bacterium that typically affects the lungs and other parts of the body, such as the brain, liver, and spinal cord. Its presence is very high in third world countries in Africa, such as Botswana and Kenya.  At least 50 percent of individuals with HIV also had TB in these two countries in 2006.

TB is more prevalent in third world countries since many people live in close proximity and have fewer medical resources available.

While it is a greater threat in developing countries, the TB bacterium is still present in the United States. In 2008, about 13,000 active TB cases were reported in the United States in both HIV-positive and -negative individuals.

Together, an HIV infection and a TB infection are so potentially fatal that the Joint United Nations Programme on HIV/AIDS (UNAIDS) commonly refers to this combination as a “co-epidemic.”

A co-epidemic is when an increased prevalence of one disease results in the spreading of another disease.

An HIV infection can cause a dormant TB infection to become active, while an infection with TB can accelerate the likelihood of developing AIDS. Infection with TB can still occur in individuals with HIV despite a high CD4 cell count, which are white blood cells that help fight infections.

There are two types of TB infections that can exist: a latent and an active infection. Latent infections lie dormant in the body and are not contagious. Usually, they produce no symptoms in the individual. However, if the individual has a weakened immune system, such as someone with HIV, a latent infection can become active.

An active infection is contagious and is usually spread in the air by coughing or sneezing. To prevent infection, it is advised that individuals stay away from people who are coughing and sneezing, wash hands frequently, and avoid settings that are more likely to have individuals with TB. These settings include hospitals, homeless shelters, and prisons. If an HIV-infected individual is found to have an active form of TB, he/she must undergo antibiotic treatment immediately.

UNAIDS estimated that an active, untreated TB infection will infect 10 -15 other people each year.

A multi-resistant strain of TB is also on the rise. This is defined as a strain that is resistant to two or more primarily used antibiotics. In cases of multi-resistant strains, other antibiotics can be given, but they are often more costly and less effective.

A multi-resistant strain is a greater threat in individuals with HIV because of their weakened immune system.

Testing

The CDC recommends an individual with HIV get tested for TB immediately upon being diagnosed with HIV. It is also recommended that an individual get retested for TB once every year; for those who are exposed to high risk settings, this test may be ordered more frequently.

The most common test for TB is a skin test. A small amount of bacterial protein is injected under the skin on the arm. A positive test will result in a hardened, raised area at the site of infection. An individual should not interpret these results himself, and should have the results read by a healthcare worker 48-72 hours after the test was administered.

A positive test, however, does not indicate whether the infection is active or latent.

Symptoms of an active infection include a persistent cough that lasts longer than two weeks, chest congestion, coughing up blood or mucus, fatigue, and weight loss.

To determine whether an active infection exists, an x-ray may be used to see whether an infection is present in the lungs. If an x-ray shows scarring or hardening in the lungs, this may suggest a latent infection.

A suspicious x-ray may require further tests, such as a culture of mucus from the lungs. This test can take several weeks to yield results.

Treatment

Individuals with HIV and an active TB infection will usually undergo treatment with a combination of four drugs: isoniazid (Niazid), rifampin (Rifadin), pyrazinamide, and ethambutol (Myambutol). Previously prescribed antiretroviral medication will usually be continued during this treatment.

This combination is given daily for two months. Isoniazid and rifampin are then administered daily or biweekly for the remaining four months.

Patients experiencing sensitivity to rifampin will be given the same regimen, except streptomycin will replace rifampin. These will be given for two months and then isoniazid, streptomycin and pyrazinamide will be administered for the remaining seven months.

According to a study published in AIDS (abstract), co-treatment of TB and HIV (with the use of HAART medication, which is a combination or three or more antiretroviral medications) resulted in a decreased viral load and an increase in CD4 cells.

However, according to an article in the American Journal of Respiratory and Critical Care Medicine, isoniazid can cause liver and kidney damage. Another major cause for concern is with the use of rifampin.

Use of this drug with HIV protease inhibitors or non-nucleoside reverse transcriptase inhibitors can diminish the effectiveness of these antiretroviral drugs. In addition, HIV medication can increase the levels of TB medications in the blood to toxic levels.

The researchers also note that high rates of adverse side effects occurred with combined treatment. Fifty-four percent of individuals experienced adverse reactions, with the most common being gastrointestinal disturbances and neuropathy, which is a loss of sensation and inability to control muscles as a result of neurological problems.

Researchers also acknowledge that physicians may choose to delay HAART medications, if feasible, until TB treatment is complete.

With immediate treatment, active TB infections can be cured. However, this co-epidemic is still a serious problem in developing countries. Getting treatment to people in need is a great challenge.

In 1994, the World Health Organization launched a five-point strategy called Directly Observed Treatment Short. Workers are currently drafting new protocols that will be implemented in 2015 to more effectively reduce the co-epidemic that exists in many third-world countries.

For more information on HIV and TB, please see the factsheet at the Centers for Disease Control and Prevention Web site.