AIDS and HIV opportunistic infections: Tuberculosis

Tuberculosis (TB) is a serious disease that spreads through the air. It is caused by a bacterium called Mycobacterium tuberculosis. Tuberculosis usually affects the lungs. However, it can affect other parts of the body, such as the kidneys or spine. Currently in the UK, about 8,500 new cases of TB are diagnosed each year.

The risk is great, however, for people who are HIV-positive. That's because tuberculosis takes advantage of a weakened immune system, which is why it's called an opportunistic infection. Worldwide, tuberculosis is the leading cause of death for people infected with HIV (human immunodeficiency syndrome). If you are HIV-positive, you should be tested for tuberculosis. Prevention and treatment not only help control tuberculosis, but also help to prevent greater damage to your immune system.

How you can get tuberculosis

The bacteria that cause tuberculosis travel through the air, such as in a cough or sneeze. But you are not likely to get the disease from a single exposure. And you can't get it from sharing dishes or utensils, or by touching someone who has it.

You are more likely to get tuberculosis from constant exposure to an infected person, such as someone with whom you work or live. You are likely to get tuberculosis in places with poor ventilation, or crowded conditions. If you are HIV-positive, discuss with your doctor whether it is safe to continue working in places like these:

• A hospital, clinic, or doctor's office
• A nursing home
• A prison
• A shelter for homeless people

Types of tuberculosis infection

There are two types of tuberculosis infection, latent and active.

• If you have a latent infection, the germs remain in your body, but don't cause symptoms.
• If your immune system is weak, the germs can multiply and become active, causing symptoms and disease.

Active disease is more likely if you have HIV, especially if your CD4 count is under 200. (CD4 cells are a type of immune system cell.) However, active tuberculosis can happen no matter what your CD4 level is. If you are infected with both HIV and TB, you are at least 10 times more likely to develop active TB than someone without HIV. If you have both infections, you have Aids (acquired immunodeficiency syndrome), a more advanced stage of HIV.

These are other factors that can increase your risk for active tuberculosis:

• Pregnancy
• Poor nutrition
• Alcohol or injection drug use

Being young or old.

Signs and symptoms of tuberculosis

These are common signs and symptoms of tuberculosis:

• A cough that lasts for more than 2-3 weeks
• Coughing up phlegm or blood
• Chest pain
• Weakness or fatigue
• Weight loss
• Lack of appetite
• Fever or chills
• Night sweats

Diagnosing tuberculosis

As soon as you know you have HIV, ask your doctor for a tuberculin skin test (Mantoux test). This involves your being injected with a substance called PPD tuberculin. If you have a latent TB infection, your skin will be sensitive to PFD tuberculin, and a hard red lump will develop at the site of the injection, usually within 48-72 hours of having the test. It can be difficult to diagnose tuberculosis for these reasons:

• If you've recently been infected with tuberculosis or if your immune system is very damaged, you may not test positive but still be infected.
• You may test positive, but have a related bacterial infection, not tuberculosis. You may need to have other tests to confirm whether you have active TB.
• Other tests you may need include:
• A chest X-ray, which produces a picture of your lungs.
• A TB smear test, where your doctor takes a sample of phlegm and examines it under a microscope for signs of bacteria.
• A sputum culture, which involves growing the bacteria to reveal signs of active tuberculosis.

If you test negative, you should be retested once a year. If you had a baby after you became HIV-positive, have your baby tested at 9 to 12 months of age.