Tuberculosis

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Tuberculosis (TB) is an infection of the lungs and respiratory system. One third of the world's people are infected with TB, and along with HIV, TB is one of the world's leading causes of death due to disease. The US Centers for Disease Control and Prevention (CDC) reports that, in 2011, close to nine million people became sick with TB and over 1.4 million died from TB worldwide. The World Health Organization (WHO) estimates that 2.9 million women became sick with TB in 2012.

In the US, the number of new TB cases reported each year has been going down since 1993. According to the CDC, the number of TB cases reported in 2012 was the lowest that is has been since reporting began in 1953.

TB is caused by a bacterium called Mycobacterium tuberculosis. It spreads from person to person when an infected person coughs, sneezes, laughs, or spits. Tiny droplets of fluid from the lungs are carried in the air and can be breathed in by someone nearby. Although it can affect many parts of the body, TB usually occurs in the lungs.

Forms of TB

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

  • Latent TB - Most people with healthy immune systems can fight off TB bacteria, even after they breathe them in and are infected. People with latent or inactive TB have no symptoms. They neither feel sick nor spread the disease to other people. In some people, TB stays latent or inactive for their entire lives. 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.

TB and HIV

People with weakened immune systems are more likely to develop active TB disease. This includes people living with HIV (HIV+), children, elderly people, and people who take drugs that suppress the immune system. Research shows that people living with HIV are at least ten times more likely to develop active TB disease than HIV-negative people. You can develop active TB with any CD4 count. Studies also show that TB can worsen HIV disease progression. Having active TB disease while HIV+ is an AIDS-defining condition.

Worldwide, TB is the leading cause of death in HIV+ people. The WHO estimates that one third of the 40 million people living with HIV worldwide are infected with TB. The CDC recommends that you be screened every year for TB if you are HIV+ by having a skin or blood test (see "Diagnosing TB," below).

Preventing TB

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, people living 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 (see "TB Treatment" below), they usually cannot spread the disease after two to three weeks on treatment.

People with active TB should be separated from others 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 Symptoms

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 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 two to three weeks
  • Coughing up sputum (phlegm) or blood
  • Unexplained weight loss
  • Fever or chills
  • Night sweats
  • Fatigue (unusual tiredness)
  • Loss of appetite
  • Chest pain

Finding and Diagnosing TB

It is recommended that HIV+ people get screened for TB once a year using a skin or blood test. The skin test is called a TST (tuberculin skin test) or PPD (purified protein derivative). A small amount of "tuberculin" (a TB protein) is injected under the skin of the arm, and the test is checked or "read" two to three days later by a health care worker who looks at the spot on the arm and measures any swelling. The test is positive if the area develops a hard swelling under the skin that is bigger than 5mm.

There is also a TB blood test, called an IGRA (interferon-gamma release assay), which measures your immune response to TB. Because HIV+ people sometimes do not develop a positive TB skin test reaction even if they are infected, the TB blood test is now the preferred test for those living with HIV. An added benefit to the IGRA test is that there is no need to return to a health clinic; results are usually available within 24 hours and can be communicated by phone.

A positive TB skin or blood test shows that you have been exposed to TB, but it does not mean you have active TB disease. Your health care provider will look at your symptoms as well as other tests, such as chest X-rays and sputum tests, before diagnosing you with active TB disease.

TB Treatment

There are two types of treatment for TB:

Preventive Treatment

During the nine months of INH and B6 treatment, your provider will draw lab tests to check for any side effects from the INH medication, such as liver inflammation. The first set of lab tests will be done after you have taken the medication for one month. Also, your provider will question you regularly about any side effects you may be having from the INH. Possible side effects from INH include:

  • loss of appetite
  • nausea and/or abdominal pain
  • jaundice (yellowing of the skin, eyes, and mucous membranes)
  • dark urine
  • rash
  • numbness and tingling of your hands and/or feet (peripheral neuropathy)
  • fever and weakness for more than three days
  • muscle soreness
  • long-lasting fatigue (extreme tiredness)

The pyroxidine or B6 medication is taken to prevent the peripheral neuropathy symptoms. It is important not to drink alcohol while you are taking INH, or your liver may become badly damaged.

In HIV+ people who are not on HIV drugs, a shorter treatment regimen has been recommended by the CDC: a combination of INH and rifapentine taken once a week for 12 weeks with DOT.  Your health care provider will help you decide which treatment option is best for you. 

Treatment of Active Disease

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

  • Isoniazid (INH)
  • Rifampin (also known as rifampicin, Rifadin, or Rimactane)
  • Pyrazinamide
  • Ethambutol (Myambutol)

These four drugs are taken daily for two months. Tests can be done to see how well the drugs are fighting the TB. If the drugs are fighting the TB well, then the treatment changes to just two drugs: isoniazid plus rifampin for four more months. Sometimes the treatment will last longer, depending on whether or not the TB is resistant to these drugs, or if the TB disease has spread through the bloodstream to other parts of the body.

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 health care provider may make changes to your TB drugs. Your provider may also 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.

As with HIV, taking your TB drugs exactly as prescribed (good adherence) is very important. The full course of treatment must be completed, even if you feel better before you have finished taking all your drugs (symptoms usually improve after three to four weeks). This helps prevent TB from coming back and becoming resistant to drugs.

Drug Resistant TB

Like HIV, TB can change to become resistant to drugs, especially if a drug is used alone. This can cause the drugs to stop working. Therefore, it is important for your provider to test your TB for drug resistance. Drug-resistant tuberculosis (DR TB) must be treated with a combination of drugs. Some TB strains are now resistant to several different drugs. These strains are called multiple-drug resistant tuberculosis (MDR TB) and extensively-drug resistant tuberculosis (XDR TB). XDR TB is resistant to almost all medications used to treat TB. As a result, many more people with XDR TB die or have treatment failure.

TB and Pregnancy

According to the CDC, untreated TB is a greater threat to pregnant women and their babies than TB treatment. Therefore, it is important to screen for and treat TB in pregnant women. Both the TB skin test and the TB blood test are safe during pregnancy. As with anyone who is not pregnant, additional tests are needed to determine if someone who tests positive for TB with a skin or blood test has active TB disease.

For pregnant women with latent or inactive TB, INH taken daily or twice weekly at a higher dose for nine months is the usual treatment. In pregnant women with active TB disease, the usual treatment is INH, rifampin, and ethambutol daily for two months followed by INH plus rifampin for seven months (for a total of nine months of treatment). It is important for pregnant women taking INH to take pyridoxine (vitamin B6) daily to help prevent nerve damage. 

Pregnant women should not take streptomycin because it can cause deafness in babies. Pyrazinamide is most often not recommended during pregnancy, as its effects on the developing baby are not yet known. Other TB drugs that should be avoided during pregnancy include: kanamycin, amikacin, capreomycin, and fluoroquinolones (an entire group or type of antibiotics).

The Bottom Line

TB is a serious disease that is the leading cause of death in HIV+ people worldwide. Many people can keep TB under control and have latent, or inactive, disease. But people with weakened immune systems, including people living with HIV, 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 of drugs, since using only one drug can lead to resistance. With both TB and HIV, good adherence is a very important factor in successful treatment. But unlike HIV, TB can usually be completely cured after less than a year of treatment.

Additional Resources

Select the links below for additional material related to tuberculosis.

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