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Medically reviewed by Last updated on Mar 22, 2023.


Tuberculosis (TB) is a serious illness that mainly affects the lungs. The germs that cause tuberculosis are a type of bacteria.

Tuberculosis can spread when a person with the illness coughs, sneezes or sings. This can put tiny droplets with the germs into the air. Another person can then breathe in the droplets, and the germs enter the lungs.

Tuberculosis spreads easily where people gather in crowds or where people live in crowded conditions. People with HIV/AIDS and other people with weakened immune systems have a higher risk of catching tuberculosis than people with typical immune systems.

Drugs called antibiotics can treat tuberculosis. But some forms of the bacteria no longer respond well to treatments.


When TB germs survive and multiply in the lungs, it is called a TB infection. A TB infection may be in one of three stages. Symptoms are different in each stage.

Primary TB infection. The first stage is called the primary infection. Immune system cells find and capture the germs. The immune system may completely destroy the germs. But some captured germs may still survive and multiply.

Most people don't have symptoms during a primary infection. Some people may get flu-like symptoms, such as:

Latent TB infection. Primary infection is usually followed by the stage called latent TB infection. Immune system cells build a wall around lung tissue with TB germs. The germs can't do any more harm if the immune system keeps them under control. But the germs survive. There are no symptoms during latent TB infection.

Active TB disease. Active TB disease happens when the immune system can't control an infection. Germs cause disease throughout the lungs or other parts of the body. Active TB disease may happen right after primary infection. But it usually happens after months or years of latent TB infection.

Symptoms of active TB disease in the lungs usually begin gradually and worsen over a few weeks. They may include:

Active TB disease outside the lungs. TB infection can spread from the lungs to other parts of the body. This is called extrapulmonary tuberculosis. Symptoms vary depending on what part of the body is infected. Common symptoms may include:

Active TB disease in the voice box is outside the lungs, but it has symptoms more like disease in the lungs.

Common sites of active TB disease outside the lungs include:

Active TB disease in children. Symptoms of active TB disease in children vary. Typically, symptoms by age may include the following:

When to see a doctor

The symptoms of tuberculosis are similar to symptoms of many different illnesses. See your health care provider if you have symptoms that don't improve with a few days of rest.

Get emergency care if you have:

Get immediate or urgent care if you:


Tuberculosis is caused by a bacterium called Mycobacterium tuberculosis.

People with active TB disease in the lungs or voice box can spread the disease. They release tiny droplets that carry the bacteria through the air. This can happen when they're speaking, singing, laughing, coughing or sneezing. A person can get an infection after inhaling the droplets.

The disease is more likely to spread when people spend a lot of time together in an indoor space. So the disease spreads easily in places where people live or work together for long periods. Also, the disease spreads more easily in crowded gatherings.

A person with a latent TB infection cannot pass the disease to other people. A person taking drugs to treat active TB disease usually can't pass the disease after 2 to 3 weeks of treatment.

Drug-resistant TB

Some forms of the TB bacteria have become drug resistant. This means that drugs that once cured the disease no longer work.

This happens, in part, because of naturally occurring genetic changes in bacteria. A random genetic change in a bacterium might give it some quality that makes it more likely to survive the attack of an antibiotic. If it does survive, then it can multiply.

When antibiotic drugs aren't used correctly — or drugs fail to kill all the bacteria for another reason — the conditions are ideal for more-resistant versions of the bacteria to get established and multiply. If these bacteria are passed on to other people, a new drug-resistant strain can grow over time.

Problems that can lead to such drug-resistant strains of bacteria include the following:

Risk factors

Anyone can get tuberculosis, but certain factors increase the risk of getting an infection. Other factors increase the risk of an infection becoming active TB disease.

The Centers for Disease Control and Prevention recommends a TB test for people who have an increased risk of TB infection or active TB disease. Talk to your health care provider if you have one or more of the following risk factors.

Risk of TB infection

Certain living or working conditions make it easier for the disease to pass from one person to another. These conditions increase the risk of getting a TB infection:

Risk of active TB disease

A weakened immune system increases the risk of a TB infection becoming active TB disease. Conditions or treatments that weaken the immune system include:

Age and active TB disease

The risk of a TB infection becoming active TB disease changes with age.


If you test positive for latent TB infection, you may need to take drugs to prevent active TB disease.

Preventing the spread of disease

If you have active TB disease, you'll need to take steps to prevent other people from getting an infection. You will take drugs for four, six or nine months. Take all of the drugs as directed during the entire time.

During the first 2 to 3 weeks, you will be able to pass TB bacteria to others. Protect others with these steps:


In countries where tuberculosis is common, infants often are vaccinated with the bacille Calmette-Guerin (BCG) vaccine. This protects infants and toddlers who are more likely to have active TB disease in the fluid surrounding the brain and spinal cord.

The vaccine may not protect against disease in the lungs, which is more likely in the United States. Dozens of new TB vaccines are in various stages of development and testing.


To diagnosis a tuberculosis (TB) infection, your health care provider will do an exam that includes:

TB tests

Your health care provider will order tests if:

Your provider will determine whether a skin test or blood test is the best option.

Skin test

A tiny amount of a substance called tuberculin is injected just below the skin on the inside of one forearm. Within 48 to 72 hours, a health care worker will check your arm for swelling at the injection site. The size of the raised skin is used to determine a positive or negative test.

This test is seeing if your immune system reacts, or has made an antibody, to tuberculosis. A positive test indicates you likely have either a latent TB infection or active TB disease. People who had a TB vaccination might get a positive test even if they have no infection.

A negative test means that your body didn't react to the test. It doesn't necessarily mean you don't have an infection.

Blood tests

A sample of blood is sent to a lab. One lab test finds out whether certain immune system cells can "recognize" tuberculosis. A positive test shows that you have either a latent TB infection or active TB disease. Other tests of the blood sample can help determine if you have active disease.

A negative result means you likely do not have a TB infection.


A chest X-ray can show irregular patches in the lungs that are typical of active TB disease.

Sputum tests

Your health care provider may take a sample of the mucus that comes up when you cough, also called sputum. If you have active TB disease in your lungs or voice box, lab tests can detect the bacteria.

A relatively quick laboratory test can tell if the sputum likely has the TB bacteria. But it may be showing bacteria with similar features.

Another lab test can confirm the presence of TB bacteria. The results often take several weeks. A lab test also can tell if it's a drug-resistant form of the bacteria. This information helps your health care provider choose the best treatment.

Other lab tests

Other lab tests that may be ordered include:


If you have a latent TB infection, your health care provider may begin drug treatments. This is especially true for people with HIV/AIDS or other factors that increase the risk of active TB disease. Most latent TB infections are treated for three or four months.

Active TB disease may be treated for four, six or nine months. Specialists in TB treatment will determine which drugs are best for you.

You will have regular appointments to see if you're improving and to watch for side effects.

Take all of the drugs

It is important to take every dose as instructed. And you must complete the full course of treatment. This is important for killing the bacteria in your body and preventing new drug-resistant bacteria.

Your public health department may use a program called directly observed therapy (DOT). With DOT, a health care worker visits you at home to watch you take your dose of drugs.

Some health care departments have programs that let you take your drugs on your own. The Centers for Disease Control and Prevention has printable forms you can use to keep track of your daily doses.

Most common TB drugs

If you have a latent TB infection, you might need to take only one or two types of drugs. Active TB disease requires taking several drugs. Common medications used to treat tuberculosis include:

You may be prescribed other drugs if you have drug-resistant tuberculosis or other complications from your illness.

Medication side effects

Most people can take TB drugs without serious side effects. If you have serious side effects, your care provider may ask you to stop taking a drug. You may have to change the dose of a drug.

Talk to your health care provider if you experience any of the following:

It is important for you to list all drugs, dietary supplements or herbal remedies you take. You may need to stop taking some of these during your treatment.

Coping and support

The long treatment plan for tuberculosis can be challenging. Anger or frustration are normal. Talking to someone, such as a therapist, might help you develop coping strategies.

Preparing for your appointment

You are likely to start with an appointment with your health care provider. You may be referred to a doctor who specializes in treating infectious diseases.

What you can do

When you make the appointment, ask if there's anything you need to do in advance. Make a list of:

For tuberculosis, some basic questions to ask your doctor include:

What to expect from your doctor

Be prepared to answer the following questions during your appointments:

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