Tuberculosis (TB) is an infectious respiratory disease of the lungs and respiratory system. Along with HIV, TB is the one of the world’s leading causes of death due to disease. It is estimated that 10-15 million people in the U.S. are infected with TB. And the disease is much more common in developing countries, in some parts of Asia and Africa.

TB is caused by bacteria. Usually the bacteria are spread from person to person when an infected person coughs, and the other person breathes in those bacteria. Although it can affect many parts of the body, TB usually attacks the lungs.

Not everyone who is infected with TB bacteria develops “active” disease.

• Latent TB
  Most people with healthy immune systems can fight the TB bacteria, even after they breathe it in and are infected. People with latent, or inactive, TB have no symptoms. They don’t feel sick and they don’t spread the disease to other people. In some people TB remains latent or inactive for their entire life. But in other people, latent TB turns into active disease if their immune system is damaged or weakened, through things like HIV infection, cancer, or transplant surgery that requires taking drugs to suppress the immune system
• Active TB
  Some people infected with TB develop active disease. Active TB usually causes symptoms like coughing and weight loss. People with active TB can spread it to others. Active TB may develop either soon after infection or years later when a person’s immune system becomes weaker

People with weakened immune systems are more likely to develop active TB disease. This includes HIV+ people, children, elderly people, and people who take drugs that suppress their immune system. Research shows that people with HIV are at least ten times more likely to develop active TB disease. You can develop active TB with any CD4 cell level. Studies show that TB can worsen HIV disease progression. Worldwide, TB is the leading cause of death in HIV+ people. The U.S. government recommends that you should be screened regularly for TB if you are HIV+ by having a skin test or an x-ray (see “Diagnosing TB,” below).

TB is spread through the air when an infected person coughs, sneezes or spits. It usually takes a long time for TB transmission to occur. Family members of people with TB, or people living for a while in the same house, health-care workers, and people who live in residential facilities like homeless shelters and prisons are most likely to get TB. People with latent (not active) TB do not spread the disease. Once a person with active TB starts treatment (drugs, more below in “TB Treatment”), they usually can’t spread the disease after 2-3 weeks on treatment.

People with active TB should be isolated until they can no longer spread the disease. If you have TB or spend time around people with TB, wear a disposable face mask. Certain types of air filters can trap the TB bacteria, and ultraviolet light can kill it.

TB is diagnosed using a skin test. A small amount of “tuberculin” (a purified TB protein) is injected under the skin of the arm, and the test is “read” 2-3 days later, by a technician who looks at that spot on the arm to see how it looks. The test is positive if the area turns red or develops a hard swelling. (But don’t try to “read” it yourself; only a trained technician can really tell you what the test means.) A positive TB skin test shows that you have been exposed to TB, but it does not mean you have active TB disease. Other tests, including chest X-rays and lung fluid tests, are needed to show whether a person with a positive skin test has active disease. Sometimes HIV+ people who have weak immune systems do not develop a positive TB skin test reaction even if they are infected (making having an X-ray more important).

After TB bacteria are inhaled, they settle in the lungs. People with healthy immune systems can usually fight the bacteria and keep it from multiplying. The immune system may build structures that actually wall off the bacteria. These structures can burst, leaving scars in the lungs. If a person’s immune system is too weak and the structures burst, the bacteria can get out and enter the bloodstream. Once in the bloodstream they travel to other parts of the body including the brain, kidneys, and bones. This is called “extrapulmonary TB.” Extrapulmonary TB is more likely in people with advanced HIV disease.

People with active TB disease may develop symptoms including:

• Cough lasting more than 2-3 weeks
• Coughing up sputum (phlegm) or blood
• Chest pain
• Fever or chills
• Night sweats
• Fatigue (unusual tiredness)
• Loss of appetite
• Wasting (excessive weight loss)

There are two types of treatment for TB:

People who have latent TB can be treated with TB drugs to prevent them from developing active disease. The usual treatments are either:

• Isoniazid (INH) daily or twice weekly for 6-9 months
• Rifampin plus pyrazinamide for two months

Treatment of active TB requires combination therapy. The usual regimen is:

• Isoniazid
• Rifampin (also known as rifampicin, Rifadin, or Rimactane)
• Pyrazinamide
• Either Myambutol (ethambutol) or streptomycin

These four drugs are taken daily for two months. (You can take tests to see how the drugs are doing. If testing shows that TB is responding to isoniazid and rifampin, Myambutol or streptomycin can be stopped.) This is followed by just isoniazid plus rifampin for four more months. A newer drug, Priftin (rifapentine) lasts longer and can be taken just once weekly. Combination pills called Rifamate (isoniazid plus rifampin) and Rifater (isoniazid, rifampin, and pyrazinamide) can reduce the number of pills you must take each day.

TB drugs can cause some side effects. For example, isoniazid can cause nerve damage (peripheral neuropathy) or liver damage, and Myambutol can cause vision problems. It is important not to drink alcohol while taking isoniazid, otherwise you can badly damage your liver. Pregnant women should not take streptomycin because it can cause deafness in their babies. There is not enough research yet to know whether pyrazinamide is safe during pregnancy.

Some TB drugs can interact with HIV drugs. Rifampin, for example, can interfere with protease inhibitors and non-nucleoside reverse transcriptase inhibitors. This can make it difficult to treat both diseases at the same time. If you are taking a protease inhibitor, your doctor may substitute Mycobutin (rifabutin) for rifampin, but this requires longer treatment and careful monitoring. Your doctor may adjust your drug doses when you are being treated for both TB and HIV. Some HIV+ people may need longer TB treatment than people without HIV.

Like HIV, TB can mutate to become resistant to drugs, especially if a drug is used alone. This can cause the drugs to stop working. For this reason, TB must be treated with a combination of drugs. Some people are infected with TB that is already resistant to multiple drugs (called multidrug-resistant TB, or MDR-TB). MDR-TB must be treated for a longer time with more drugs.

As with HIV, taking your drugs exactly as prescribed (good adherence) to TB treatment is very important. The full course of treatment must be completed, even if you feel better before it’s finished (symptoms usually improve after 3-4 weeks). This helps prevent TB from coming back(relapsing) or becoming resistant to drugs. Because some people find it difficult to complete their treatment—and because TB is easily spread to others— sometimes “directly observed therapy” (DOT) is used. With DOT, a nurse, outreach worker, or family member makes sure the person with TB takes their pills each day.

TB is a serious disease that is the leading cause of death in HIV+ people worldwide. Many people can keep their TB under control and have latent, or inactive, disease. But people with weakened immune systems—including HIV+ people—are much more likely to develop active TB disease that needs treatment. In many ways, TB and HIV treatment are similar. Both diseases must be treated with a combination drug regimen, since using one medication alone (monotherapy) isn’t good because it can cause the drugs to stop working (quickly lead to drug resistance). With both TB and HIV, good adherence is an important factor in successful treatment. But unlike HIV, TB can usually be completely cured after less than a year of treatment.

1		American Thoracic Society, Centers for Disease Control and Prevention, & Infectious Diseases Society of America. (2003). Treatment of tuberculosis. CDC Morbidity and Mortality Weekly Report, 52(RR11): Retrieved July 2003 from http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5211a1.htm.
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