Although your body may harbor the bacteria that cause tuberculosis, your immune system often can prevent you from becoming sick. For this reason, doctors make a distinction between:

• Latent TB. In this condition, you have a TB infection, but the bacteria remain in your body in an inactive state and cause no symptoms. Latent TB, also called inactive TB or TB infection, isn't contagious.
• Active TB. This condition makes you sick and can spread to others.

Signs and symptoms of active TB include:

• Unexplained weight loss
• Fatigue
• Fever
• Night sweats
• Chills
• Loss of appetite

Tuberculosis usually attacks your lungs. Signs and symptoms of TB of the lungs include:

• Coughing that lasts three or more weeks
• Coughing up blood
• Chest pain, or pain with breathing or coughing

Tuberculosis can also affect other parts of your body, including your kidneys, spine or brain. When TB occurs outside your lungs, symptoms vary according to the organs involved. For example, tuberculosis of the spine may give you back pain, and tuberculosis in your kidneys might cause blood in your urine.

When to see a doctor
See your doctor if you have a fever, unexplained weight loss, night sweats and a persistent cough. These are often signs of TB, but they can also result from other medical problems. Your doctor can perform tests to help determine the cause. TB can be diagnosed by your primary care doctor or by a doctor who specializes in lung diseases (pulmonologist) or by an infectious disease specialist. If you don't have a doctor, your local public health department can help.

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Tuberculosis is caused by an organism called Mycobacterium tuberculosis. The bacteria spread from person to person through microscopic droplets released into the air. This can happen when someone with the untreated, active form of tuberculosis coughs, speaks, sneezes, spits, laughs or sings. Rarely, a pregnant woman with active TB may pass the bacteria to her unborn child.

Although tuberculosis is contagious, it's not especially easy to catch. You're much more likely to get tuberculosis from a family member or close co-worker than from a stranger. Most people with active TB who've had appropriate drug treatment for at least two weeks are no longer contagious.

TB infection vs. active TB
If you breathe TB bacteria into your lungs, one of four things might happen:

• You don't become infected with TB. Your immune system immediately destroys the germs and clears them from your body.
• You develop latent TB infection. The germs settle in your lungs and begin to multiply. Within several weeks, however, your immune system successfully "walls off" the bacteria in your lungs, much like a scab forming over a wound. The bacteria may remain within these walls for years — alive, but in a dormant state. In this case, you're considered to have TB infection and you'll test positive on a TB skin test. But you won't have symptoms and won't transmit the disease to others.

• You develop active TB. If your immune defenses fail, TB bacteria begin to exploit your immune system cells for their own survival. The bacteria move into the airways in your lungs, causing large air spaces (cavities) to form. Filled with oxygen — which the bacteria need to survive — the air spaces make an ideal breeding ground for the bacteria. The bacteria may then spread from the cavities to the rest of your lungs as well as to other parts of your body.

  If you have active TB, you're likely to feel sick. Even if you don't feel sick, you can still infect others. Without treatment, many people with active TB die. Those who survive may develop long-term symptoms, such as chest pain and a cough with bloody sputum, or they may recover and go into remission.

• You develop active TB years after the initial infection. After you've had latent TB for years, the walled-off bacteria may suddenly begin multiplying again, causing active TB, also known as reactivation TB. It's not always clear what triggers this reactivation, but it most commonly happens after your immune system becomes weakened. Your resistance may be lower because of aging, drug or alcohol abuse, malnutrition, chemotherapy, prolonged use of prescription medications such as corticosteroids or TNF inhibitors, and diseases such as HIV/AIDS.

Only about one in 10 people who have TB infection goes on to develop active TB. The risk is greatest in the first two years after infection and is much higher if you have HIV infection.

HIV and TB
Since the 1980s, the number of cases of tuberculosis has increased dramatically because of the spread of HIV, the virus that causes AIDS. Tuberculosis and HIV have a deadly relationship — each drives the progress of the other.

Infection with HIV suppresses the immune system, making it difficult for the body to control TB bacteria. As a result, people with HIV are many times more likely to get TB and to progress from latent to active disease than are people who aren't HIV-positive.

TB is one of the leading causes of death among people with AIDS, especially outside the United States.  One of the first indications of HIV infection may be the sudden onset of TB, often in a site outside the lungs.

Drug-resistant TB
Another reason TB remains a major killer is the increase in drug-resistant strains of the bacterium. Ever since the first antibiotics were used to fight TB 60 years ago, the germ has developed the ability to survive attack, and that ability gets passed on to its descendants. Drug-resistant strains of TB emerge when an antibiotic fails to kill all of the bacteria it targets. The surviving bacteria become resistant to that particular drug and frequently other antibiotics as well. Today, for each major TB medication, there's a TB strain that resists its treatment.

The major cause of TB drug resistance is inadequate treatment, either because the wrong drugs are prescribed or because people don't take their entire course of medication.

There are two types of drug-resistant TB:

• Multidrug-resistant TB (MDR TB). This form of TB can't be killed by the two most powerful antibiotics for TB, isoniazid and rifampin. Although MDR TB can be successfully treated, it's much harder to combat than is regular TB and requires long-term therapy — up to two years — with drugs that are very expensive and can cause serious side effects. People with untreated MDR TB can transmit this serious type of TB to others.
• Extensively drug-resistant TB (XDR TB). XDR TB is a less common form of MDR TB in which the bacteria resist isoniazid and rifampin as well as most of the alternative or second line drugs used to treat TB. XDR TB has shown up across the world, including 49 cases in the United States between 1993 and 2006. Treatment for XDR TB is challenging and lengthy and leads to serious side effects and a higher rate of failure. Recently, the first cases of completely drug-resistant TB were reported — the bacteria could not be killed by any available TB drug.

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Anyone can get tuberculosis, but certain factors increase your risk of the disease. These factors include:

• Lowered immunity. A healthy immune system can often successfully fight TB bacteria, but your body can't mount an effective defense if your resistance is low. A number of factors can weaken your immune system. Having a disease that suppresses immunity, such as HIV/AIDS, diabetes, end-stage kidney disease, certain cancers or the lung disease silicosis, can reduce your body's ability to protect itself. Your risk is also higher if you take corticosteroids, certain arthritis medications, chemotherapy drugs or other drugs that suppress the immune system.
• Close contact with someone with infectious TB. In general, you must spend an extended period of time with someone with untreated, active TB to become infected yourself. You're more likely to catch the disease from a family member, roommate, friend or close co-worker.
• Country of origin. People from regions with high rates of TB — especially sub-Saharan Africa, India, China, the islands of Southeast Asia and Micronesia, and parts of the former Soviet Union — are more likely to develop TB. In the United States, more than half the people with TB were born in a different country. Among these, the most common countries of origin were Mexico, the Philippines, India and Vietnam.
• Age. Older adults are at greater risk of TB because normal aging or illness may weaken their immune systems. They're also more likely to live in nursing homes, where outbreaks of TB can occur.
• Substance abuse. Long-term drug or alcohol use weakens your immune system and makes you more vulnerable to TB.
• Malnutrition. A poor diet or one too low in calories puts you at greater risk of TB.
• Lack of medical care. If you are on a low or fixed income, live in a remote area, have recently immigrated to the United States or are homeless, you may lack access to the medical care needed to diagnose and treat TB.
• Living or working in a residential care facility. People who live or work in prisons, immigration centers or nursing homes are all at risk of TB. That's because the risk of the disease is higher anywhere there is overcrowding and poor ventilation.
• Living in a refugee camp or shelter. Weakened by poor nutrition and ill health and living in crowded, unsanitary conditions, refugees are at especially high risk of TB infection.
• Health care work. Regular contact with people who are ill increases your chances of exposure to TB bacteria. Wearing a mask and frequent hand washing greatly reduce your risk.
• International travel. As people migrate and travel widely, they may expose others or be exposed to TB bacteria.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Without treatment, tuberculosis can be fatal. Drug-resistant strains of the disease are more difficult to treat.

Untreated active disease typically affects your lungs, but it can spread to other parts of the body through your bloodstream. Complications vary according to the location of TB bacteria:

• Lung damage can occur if TB in your lungs (pulmonary TB) isn't diagnosed and treated early.
• Severe pain, abscesses and joint destruction may result from TB that infects your bones.
• Meningitis can occur if TB infects your brain and central nervous system.
• Miliary TB is TB that has spread throughout your entire body, a serious complication.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

If you suspect that you have tuberculosis, contact your family doctor, a general practitioner or your state health department. You may be referred to an infectious disease or lung specialist (pulmonologist).

You can help your doctor by being prepared with as much information as possible. Here's some information to help you get ready for your appointment.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance. In particular, ask if you should wear a face mask to your appointment.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including your HIV status (if known), country of origin, any recent travel outside the United States, contact with people who may have tuberculosis, any past infection with TB, and any medical conditions or diseases you have.
• Make a list of all medications, as well as any vitamins or supplements, that you're taking.
• Take a family member or friend along, if possible. Sometimes it can be difficult to absorb all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions ahead of time will help you make the most of your time together. For TB, some basic questions to ask your doctor include:

• What kinds of tests do I need?
• What is the best course of action?
• How long will my treatment last?
• What can I do to stay on track with my treatment?
• I have these other health conditions. How can I best manage them together?
• Are there any restrictions that I need to follow, especially with respect to preventing the spread of infection?
• Should I see a specialist? What will that cost, and will my insurance cover it?
• Is there a generic alternative to the medicine you're prescribing me?
• Are there any brochures or other printed material that I can take with me? What Web sites do you recommend?
• Will I work with a nurse or other health care provider to oversee my treatment?
• What are the side effects of my treatment?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over points you want to spend more time on. Your doctor may ask:

• When did you first begin experiencing symptoms?
• Have you been in contact with anyone who has TB?
• Were you born in another country, or have you traveled in another country?
• Have you ever had tuberculosis or a positive skin test in the past?
• What kind of work do you do?
• Do you use alcohol or recreational drugs?
• What is your typical diet?
• Do you have HIV infection or AIDS, cancer, diabetes or any other medical condition?

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

If your doctor suspects TB, you will need a complete medical evaluation and tests for TB infection.

Skin test
The most commonly used diagnostic tool for TB is a simple skin test. Although there are two methods, the Mantoux test is preferred because it's more accurate.

For the Mantoux test, a small amount of a substance called PPD tuberculin is injected just below the skin of your inside forearm. You should feel only a slight needle prick. Within 48 to 72 hours, a health care professional will check your arm for swelling at the injection site, indicating a reaction to the injected material. A hard, raised red bump (induration) means you're likely to have TB infection. The size of the bump determines whether the test results are significant, based on your risk factors for TB.

The Mantoux test isn't perfect. A false-positive test suggests that you have TB when you really don't. This is most likely to occur if you're infected with a different type of mycobacterium other than the one that causes tuberculosis, or if you've recently been vaccinated with the bacillus Calmette-Guerin (BCG) vaccine. This TB vaccine is seldom used in the United States, but widely used in countries with high TB infection rates.

On the other hand, some people who are infected with TB — including children, older people and people with AIDS — may have a delayed or no response to the Mantoux test.

Blood tests
Blood tests may be used to confirm or rule out latent or active TB. These tests use sophisticated technology to measure the immune system's reaction to Mycobacterium tuberculosis. These tests are quicker and more accurate than is the traditional skin test. They may be useful if you're at high risk of TB infection but have a negative response to the Mantoux test, or if you received the BCG vaccine.

Further testing
If the results of a TB test are positive (referred to as "significant"), you may have further tests to help determine whether you have active TB disease and whether it is a drug-resistant strain.

These tests may include:

• Chest X-ray or CT scan. If you've had a positive skin test, your doctor is likely to order a chest X-ray. In some cases, this may show white spots in your lungs where your immune system has walled off TB bacteria. In others, it may reveal a nodule or cavities in your lungs caused by active TB. A computerized tomography (CT) scan, which uses cross-sectional X-ray images, may show more subtle signs of disease.

• Culture tests. If your chest X-ray shows signs of TB, your doctor may take a sample of your stomach secretions or sputum — the mucus that comes up when you cough. The samples are tested for TB bacteria, and your doctor can have the results of special smears in a matter of hours.

  Samples may also be sent to a laboratory where they're examined under a microscope as well as placed on a special medium that encourages the growth of bacteria (culture). The bacteria that appear are then tested to see if they respond to the medications commonly used to treat TB. Your doctor uses the results of the culture tests to prescribe the most effective medications for you. Because TB bacteria grow very slowly, traditional culture tests can take four to eight weeks.

• Other tests. Testing called nuclear acid amplification (NAA) can detect genes associated with drug resistance in Mycobacterium tuberculosis. This test is generally available only in developed countries.

  A test used primarily in developing countries is called the microscopic-observation drug-susceptibility (MODS) assay. It can detect the presence of TB bacteria in sputum in as little as seven days. Additionally, the test can identify drug-resistant strains of the TB bacteria.

What if my test is negative?
Having little or no reaction to the Mantoux test usually means that you're not infected with TB bacteria. But in some cases it's possible to have TB infection in spite of a negative test. Reasons for a false-negative test include:

• Recent TB infection. It can take eight to 10 weeks after you've been infected for your body to react to a skin test. If your doctor suspects that you've been tested too soon, you may need to repeat the test in a few months.
• Severely weakened immune system. If your immune system is compromised by an illness, such as AIDS, or by corticosteroid or chemotherapy drugs, you may not respond to the Mantoux test, even though you're infected with TB. Diagnosing TB in HIV-positive people is further complicated because many symptoms of AIDS are similar to TB symptoms.
• Vaccination with a live virus. Vaccines that contain a live virus, such as the measles or smallpox vaccine, can interfere with a TB skin test.
• Overwhelming TB disease. If your body has been overwhelmed with TB bacteria, it may not be able to mount enough of a defense to respond to the skin test.
• Improper testing. Sometimes the PPD tuberculin may be injected too deeply below the surface of your skin. In that case, any reaction you have may not be visible. Be sure that you're tested by someone skilled in administering TB tests.

Diagnosing TB in children
It's harder to diagnose TB in children than in adults. Children may swallow sputum, rather than coughing it out, making it harder to take culture samples. And infants and young children may not react to the skin test. For these reasons, tests from an adult who is likely to have been the cause of the infection may be used to help diagnose TB in a child.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Medications are the cornerstone of tuberculosis treatment. But treating TB takes much longer than treating other types of bacterial infections. Normally, you take antibiotics for at least six to nine months to destroy the TB bacteria. The exact drugs and length of treatment depend on your age, overall health, possible drug resistance, the form of TB (latent or active) and its location in the body.

Several promising new TB drugs are in development, and some may become available within the next 10 years.

Treating TB infection (latent TB)
If tests show that you have TB infection but not active disease, your doctor may recommend preventive drug therapy to destroy bacteria that might become active in the future. You're likely to receive a daily or twice-a-week dose of the TB medication isoniazid. For treatment to be effective, you usually take isoniazid for nine months. Long-term use of isoniazid can cause side effects, including the life-threatening liver disease hepatitis. For this reason, your doctor will monitor you closely while you're taking isoniazid. During treatment, avoid using acetaminophen (Tylenol, others) and avoid or limit alcohol use. Both increase your risk of liver damage.

Treating active TB disease
If you're diagnosed with active TB, you're likely to begin taking four medications — isoniazid, rifampin (Rifadin), ethambutol (Myambutol) and pyrazinamide. This regimen may change if tests later show some of these drugs to be ineffective. Even so, you'll continue to take several medications. Depending on the severity of your disease and whether the bacteria are drug-resistant, one or two of the four drugs may be stopped after a few months. You may be hospitalized for the first two weeks of therapy or until tests show that you're no longer contagious.

Sometimes the drugs may be combined in a single tablet such as Rifater, which contains isoniazid, rifampin and pyrazinamide. This makes your treatment less complicated while ensuring that you get all the drugs needed to completely destroy TB bacteria. Another drug that may make treatment easier is rifapentine (Priftin), which is taken just once a week during the last four months of therapy, in combination with other drugs.

Medication side effects
Side effects of TB drugs aren't common, but can be serious when they do occur. All TB medications can be highly toxic to your liver. Rifampin can also cause severe flu-like signs and symptoms — fever, chills, muscle pain, nausea and vomiting. When taking these medications, call your doctor immediately if you experience any of the following:

• Nausea or vomiting
• Loss of appetite
• A yellow color to your skin (jaundice)
• Dark urine
• A fever that lasts three or more days and has no obvious cause
• Tenderness or soreness in your abdomen
• Blurred vision or colorblindness

Treating drug-resistant TB
Multidrug-resistant TB (MDR TB) can't be cured by the two major TB drugs, isoniazid and rifampin. Extensive drug-resistant TB (XDR TB) is resistant to those drugs as well as three or more of the second line TB drugs. Treating these resistant forms of TB is far more costly than is treating nonresistant TB.

Treatment of drug-resistant TB requires taking a "cocktail" of at least four drugs, including first line medications that are still effective and several second line medications, for 18 months to two years or longer. Even with treatment, many people with these types of TB may not survive. If treatment is successful, you may need surgery to remove areas of persistent infection or repair lung damage.

Treating people who have HIV/AIDS
HIV-positive people are especially likely to develop active TB, and drug-resistant forms of the disease are especially dangerous for them. What's more, the most powerful AIDS drugs (antiretroviral therapy) interact with rifampin and other drugs used to treat TB, reducing the effectiveness of both types of medications.

To avoid interactions, people living with both HIV and TB may stop taking antiretroviral therapy while they complete a short course of TB therapy that includes rifampin. Or they may be treated with a TB regimen in which rifampin is replaced with another drug that's less likely to interfere with AIDS medications. In such cases, doctors carefully monitor the response to therapy, and the duration and type of regimen may change over time.

Treating children and pregnant women
Treating TB in children is largely the same as treating adults, except that ethambutol is not used for young children because of the possible side effect of vision problems. Instead of ethambutol, children may take streptomycin.

For pregnant women with active TB, initial treatment often involves three drugs — isoniazid, rifampin and ethambutol. Pyrazinamide isn't recommended because its effect on the unborn baby isn't known. Some second line TB medications also aren't recommended.

Completing treatment is essential
After a few weeks, you won't be contagious and you may start to feel better. It might be tempting to stop taking your TB drugs. But it is crucial that you finish the full course of therapy and take the medications exactly as prescribed by your doctor. Stopping treatment too soon or skipping doses can allow the bacteria that are still alive to become resistant to those drugs, leading to TB that is much more dangerous and difficult to treat. Drug-resistant strains of TB can quickly become fatal, especially if your immune system is impaired.

In an effort to help people stick with their treatment, a program called directly observed therapy (DOT) is recommended. In this approach, a nurse or other health care professional administers your medication so that you don't have to remember to take it on your own. Sometimes clinics provide incentives, such as food coupons or transportation, for people to show up for their appointments.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

In general, TB is preventable. From a public health standpoint, the best way to control TB is to diagnose and treat people with TB infection before they develop active disease and to take careful precautions with people hospitalized with TB. But there also are measures you can take on your own to help protect yourself and others:

• Keep your immune system healthy. Eat plenty of healthy foods including fruits and vegetables, get enough sleep, and exercise at least 30 minutes a day most days of the week to keep your immune system in top form.
• Get tested regularly. Experts advise people who have a high risk of TB to get a skin test once a year. This includes people with HIV or other conditions that weaken the immune system, people who live or work in a prison or nursing home, health care workers, people from countries with high rates of TB, and others in high-risk groups.
• Consider preventive therapy. If you test positive for latent TB infection, your doctor will likely advise you to take medications to reduce your risk of developing active TB. Vaccination with BCG isn't recommended for general use in the United States, because it isn't very effective in adults and it causes a false-positive result on a Mantoux skin test. But the vaccine is often given to infants in countries where TB is more common. Vaccination can prevent severe TB in children. Researchers are working on developing a more effective TB vaccine.
• Finish your entire course of medication. This is the most important step you can take to protect yourself and others from TB. When you stop treatment early or skip doses, TB bacteria have a chance to develop mutations that allow them to survive the most potent TB drugs. The resulting drug-resistant strains are much more deadly and difficult to treat.

To help keep your family and friends from getting sick if you have active TB:

• Stay home. Don't go to work or school or sleep in a room with other people during the first few weeks of treatment for active TB.
• Ensure adequate ventilation. Open the windows whenever possible to let in fresh air.
• Cover your mouth. It takes two to three weeks of treatment before you're no longer contagious. During that time, be sure to cover your mouth with a tissue anytime you laugh, sneeze or cough. Put the dirty tissue in a bag, seal it and throw it away. Also, wearing a mask when you're around other people during the first three weeks of treatment may help lessen the risk of transmission.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Undergoing treatment for TB is a complicated and lengthy process. But the only way to cure the disease is to stick with your treatment. You may find it helpful to have your medication given by a nurse or other health care professional so that you don't have to remember to take it on your own. In addition, try to maintain your normal activities and hobbies and stay connected with family and friends.

Keep in mind that your physical health can affect your mental health. Denial, anger and frustration are normal when you must deal with something difficult and unexpected. At times, you may need more tools to deal with these or other emotions. Professionals, such as therapists or behavioral psychologists, can help you develop positive coping strategies.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.