Tuberculosis, or TB, is a bacterial infection caused by Mycobacterium tuberculosis (M. tb). This germ most often damages the lungs but can also infect other organs in the human body. TB is an airborne disease that spreads when M. tb is released in the air by someone with active TB. The disease becomes airborne when someone who has TB talks, sings, sneezes, or coughs.
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What Is Tuberculosis?
Tuberculosis is a disease that forms when M. tb bacteria enter and infect the body.
M. tb most often affects the lungs but can occur in almost any other organ, such as the brain, kidneys, or spine.
What are the types of tuberculosis?
There are two types of TB infections:
- Active TB disease — Occurs when the infection "breaks free" from the lung's immune cells, causing damage to the organ.
- Latent TB — Occurs when your body "walls off" the infection in the lungs, preventing symptoms from developing.
Active TB:
- Causes symptoms.
- Could spread to other parts of the body or to other people.
What causes tuberculosis?
Tuberculosis is caused by bacteria that travel through the air when someone with the disease coughs or sneezes. Active TB is contagious, but it doesn't spread from one person to another very easily.
People cannot get TB from:
- Hugging someone or shaking their hand.
- Sharing toothbrushes, food, drinks, glasses, or utensils.
- Touching bed sheets or toilet seats.
The bacteria travel through the air when someone with TB coughs, sings, sneezes, or talks. If someone breathes in air particles containing the bacteria, the TB can infect them.
After TB germs enter someone's lungs, they can grow and travel through the bloodstream — and to other organs in the body. A person with TB can only release TB germs into the air if they have the disease in their lungs or throat. A person with TB in other organs of the body, such as the kidney or brain, can't pass it on to others.
Tuberculosis risk factors
People are at risk for TB infection if they have spent time around someone else with active TB disease. Even after breathing in the bacteria, though, it may take weeks or years for a person to form active disease.
People with latent TB can't release the germs into the air. Because they cannot release bacteria into the air they cannot spread the infection to other people.
Those most at risk for TB infection include:
- Children under 5 years of age who have had a positive TB test.
- People from parts of the world with high rates of TB, such as India or parts of Asia or Africa.
- People who are homeless or live in refugee camps.
- People who have HIV or who share needles to inject drugs.
- People who spend time around others with TB.
- People who work in places where others have a high risk for TB, such as prisons, homeless shelters, or hospitals.
People with latent TB are more likely to get active TB if they have a medical condition that weakens their immune system.
This includes those who:
- Are babies or very young children.
- Have a history of cancer, especially head and neck cancer, or are receiving chemotherapy for cancer.
- Have diabetes.
- Have had an organ or bone marrow transplant.
- Have HIV.
- Have severe kidney disease (especially those on hemodialysis).
- Have silicosis — a type of lung disease.
- Have very low body weight.
- Receive certain treatments for autoimmune disorders, such as RA or IBD.
People with latent TB don't have symptoms or feel sick. But they can develop active TB if they don't receive treatment for their infection.
Complications of tuberculosis
If a person with active TB disease doesn't receive proper treatment, they can suffer severe complications or even die.
Complications can include:
- Damage to the joints, mainly the hips and knees.
- Heart problems.
- Meningitis – Swelling around the spine or brain.
- Pain in the spine and back.
- Problems in the liver or kidneys.
- Severe damage to the lungs.
How can I reduce my risk of tuberculosis?
A TB screening is the best way to reduce your risk of getting TB. Treatment for latent TB is the best way to prevent active TB disease.
How common is tuberculosis?
The American Lung Association estimates that about 13 million people in the U.S. have latent TB infection. Most people with latent TB don't develop active disease. Only about one in 10 people with latent TB will get sick with active TB at some point in their life.
The CDC reports that 565 people died of TB-related causes in the U.S. in 2022, and that there were 9,633 cases of active TB in the U.S. in 2023. These are very low numbers compared to the total population.
What Are the Signs and Symptoms of Tuberculosis?
People with latent TB most often won't have symptoms. But if you have active TB disease, you'll likely feel sick.
Symptoms include:
- Bad coughing that lasts at least three weeks.
- Coughing up blood or mucus.
- Feeling weak or tired.
- Fever, chills, or night sweats.
- Losing weight.
- Not feeling hungry.
- Pain in your chest.
When should I see a doctor about my tuberculosis?
You should see your doctor if:
- You think you had a TB exposure.
- You've been around people with TB and have the above symptoms.
- You're at higher risk for TB and develop the above symptoms.
How Do You Diagnose Tuberculosis?
If there's a chance you might have a TB infection, a health care provider will screen you.
Screening tests
A TB screening test is a blood or skin test that looks for exposure to TB bacteria within your body. A positive skin or blood test means that TB bacteria have infected you; it does not necessarily mean that you have active TB disease. However, that test alone cannot tell your doctor if there is a latent or active infection.
Blood tests
Your doctor may order the TB blood tests called interferon-gamma release assays (IGRAs). These tests measure your immune system’s response to TB bacteria in your blood. You will have some blood drawn with a needle that will be sent off to a lab. After a few days, the results will indicate whether you tested negative or positive.
Skin tests
Your doctor may order the tuberculin skin test (TST). Other names for the skin test are the Mantoux and purified protein derivative (PPD).
The first step of a skin test is receiving an injection of a small amount of fluid in the skin under your forearm. After two to three days, you'll return so the results can be read by looking at your arm. A negative test means you don't have TB bacteria in your body. A positive test means you probably do have TB bacteria.
If you test positive, your doctor may order other tests to determine if an infection is present. To test for active TB disease, your doctor will need a sample of your saliva mixed with mucus. They will also need you to get a chest x-ray.
What does TB look like on chest x-rays?
On chest X-rays, TB appears as infiltrates, which are areas in the lungs that look more opaque (whiter) than normal. These cloudy spots are warning signs that treatment is needed.
These infiltrates typically mean:
- Accumulation of immune cells, fluid, or lung tissue damage.
- Early signs of active TB, especially in the upper lobes.
- Inflammation or infection caused by the M. tb bacterium.
How Do You Treat Tuberculosis?
TB is treated with medication. Without treatment, TB can cause death by damaging the lungs and other organs in your body. It gets harder for damaged lungs to do their job and can cause fluid to build up. Your lungs can also start to fill with blood.
The more blood and fluid that builds up in the lungs, the harder it is to breathe. If treatment doesn't slow down the bacteria, a person will die from not having enough oxygen. This is why it's crucial to get treatment for TB. Your treatment will depend on whether you have latent TB or active TB.
Drug-resistant TB infections
Some people with TB can form resistance to common TB drugs. Drug resistance means certain medications can no longer harm the TB bacteria, so doctors must use a new drug that the bacteria can't fight. It's possible to form resistance to one or more TB drugs.
Your doctor will guide you in what medicine to take, depending on any drug resistance your TB disease has. If you have drug-resistant TB, it can take longer to cure the disease. For those who may form resistance to several TB drugs, a cure may not be possible.
Medicine to treat tuberculosis
Treatment for latent TB
Doctors use three medications to treat latent TB:
- Isoniazid with vitamin B6.
- Rifapentine with Isoniazid.
- Rifampin.
Here are some common treatment plans involving the above drug regimens:
- Take isoniazid and rifapentine once a week for three months (12 doses).
- Take isoniazid and rifampin every day for three months.
- Take isoniazid with vitamin B6 every day for six to nine months.
- Take rifampin every day for four months.
Treatment for latent TB is effective and reduces the risk of someone developing active TB.
Treatment for active TB
Treating active TB disease usually involves two separate stages.
The first involves taking four medications for two months:
- Isoniazid
- Ethambutol
- Pyrazinamide
- Rifampin
It's vital to take all these medications exactly as the doctor tells you to. The second stage, called the continuation stage, involves taking isoniazid and rifampin for four months. Treatment for active TB also cures the disease in most cases.
Common side effects of TB treatment
These are some common side effects of different TB drugs:
- Bruises on the skin.
- Dark-colored urine.
- Itchy skin, yellow skin, or a skin rash.
- Feeling numbness or tingling in the hands or feet.
- Loss of appetite.
- Stomach pains, nausea, vomiting, or diarrhea.
- Yellow eyes or changes in your eyesight, especially when viewing the colors red and green.
