Tuberculosis is a highly contagious bacterial infection that affects your lungs. In areas where tuberculosis is common, vaccines can offer protection.

Tuberculosis (TB), once called consumption, is a highly infectious disease that primarily affects the lungs.

According to the World Health Organization (WHO), 1.5 million people died from the disease in 2020. Tuberculosis is also the 13th leading cause of death globally. Currently, it’s the second main infectious cause of death, after COVID-19.

TB is most common in developing countries, but according to the Centers for Disease Control and Prevention (CDC), over 7,000 cases were reported in the United States in 2020.

Tuberculosis is usually curable — and preventable — under the right conditions.

Some people who acquire Mycobacterium tuberculosis, the bacterium that causes TB, do not experience symptoms. This condition is known as latent TB. TB can stay dormant for years before developing into active TB disease.

Active TB typically causes many symptoms. While symptoms usually relate to the respiratory system, they could affect other parts of the body, depending on where the TB bacteria grow.

Symptoms caused by TB in the lungs include:

General TB symptoms include:

Along with general symptoms, TB that spreads to other organs can also cause:

Risk factors that increase your chance of contracting the bacteria that causes TB disease include:

Medications that suppress the immune system can also put people at risk of developing active TB disease. These include medications that help prevent organ transplant rejection.

Other medications that increase your risk of active TB include those taken to treat:

According to the WHO, more than 95 percent of all TB-related deaths occur in developing countries.

Traveling to regions with high TB rates can also increase your risk of contracting the bacterial infection. These regions include:

  • sub-Saharan Africa
  • India
  • Mexico and other Latin American countries
  • China and many other Asian countries
  • parts of Russia and other countries of the former Soviet Union
  • islands of Southeast Asia
  • Micronesia

Many lower-income U.S. households have limited access to resources, including healthcare, needed to diagnose and treat TB, which puts them at greater risk of developing active TB disease.

People experiencing homelessness and people living in congregate settings, including jails, prisons, and correctional facilities, have a higher risk of contracting the bacterial infection.

HIV and TB

People living with HIV are at higher risk of contracting the infection and dying from TB. In fact, TB is the leading cause of death of HIV-positive people, according to the WHO.

Untreated latent TB is more likely to progress to active TB in a person living with HIV. That makes testing for TB essential for anyone with a HIV-positive status.

People living with HIV can take a few important steps to help reduce the risk of contracting this bacterial infection:

  • Getting tested for TB.
  • Taking HIV medication as advised by healthcare professionals.
  • Avoiding being in close proximity to someone with TB.
  • Trying to stop smoking — smoking can both raise the risk of developing TB and reduce the response to HIV and TB treatment.
  • Eating a nutrient-rich, balanced diet to help reduce the risk of complications from HIV and improve medication absorption.
  • Getting regular exercise, if possible, to promote immune system health.

A bacterium called Mycobacterium tuberculosis causes TB. A variety of TB strains exist, and some of these have become resistant to medication.

TB bacteria are transmitted through infected droplets in the air. Once these droplets enter the air, anyone nearby can inhale them. Someone with TB can transmit bacteria by:

  • sneezing
  • coughing
  • speaking
  • singing

People with well-functioning immune systems may not experience TB symptoms, even if they’ve contracted the bacteria. This is known as latent or inactive TB infection. About a quarter of the world’s population has latent TB.

Latent TB is not contagious, but it can become active disease over time. Active TB disease can make you sick, and you can also spread it to others.

Healthcare professionals can diagnose TB with a few different tests, including a skin test, a blood test, or both.

You may need both if:

  • a skin test is positive
  • there’s a chance you’ve received a false negative result from the skin test.

A false negative result can happen if your immune system isn’t working properly or if it’s been less than 8 weeks since exposure to TB.

Skin test

Your doctor can use a purified protein derivative (PPD) skin test to determine if you’ve acquired TB bacteria.

For this test, your doctor will inject 0.1 milliliter (mL) of PPD (a small amount of protein) under the top layer of your skin. Between 2 and 3 days later, you’ll return to your doctor’s office to have the results read.

A welt on your skin over 5 millimeters (mm) in size where the PPD was injected may be considered a positive result. Reactions between 5 and 15 mm in size can be considered positive depending on risk factors, health, and medical history. All reactions over 15 mm are considered positive, regardless of risk factors.

The test is not perfect, though. It can only tell you whether you have a TB infection, not whether you have active TB disease. Plus, some people do not respond to the test even if they have TB. Others respond to the test and do not have TB. People who’ve recently received the TB vaccine may test positive but not have a TB infection.

Blood test

Your doctor can use a blood test to follow up on TB skin results. They may also recommend a blood test first, particularly if you have an existing health condition that may affect your response to the skin test.

The two TB blood tests currently approved in the U.S. are Quantiferon and T-Spot. Blood tests results can be positive, negative, or indeterminate. Like the skin test, the blood test can’t indicate whether or not you have active TB disease.

Chest X-ray

If you get a positive result from the skin or blood test, your doctor will likely order a chest X-ray to look for certain small spots in your lungs. These spots, a sign of a TB infection, indicate that your body is trying to isolate the TB bacteria.

A negative chest X-ray can suggest latent TB, but it’s also possible your test results were incorrect. Your doctor may recommend other testing.

If the test indicates you have active TB disease, you will begin treatment for active TB. Otherwise, your doctor may recommend getting treated for latent TB. This can prevent the bacteria from reactivating and making you sick in the future.

Other tests

Your doctor may also order tests on sputum or mucus extracted from deep inside your lungs to check for TB bacteria. If your sputum tests positive, this means you can transmit TB bacteria to others. You’ll need to wear a special mask until after you’ve started treatment and your sputum tests negative for TB.

You may need other tests, such as a chest CT scan, bronchoscopy, or lung biopsy, if previous test results remain unclear.

Many bacterial infections improve after a week or two of treatment with antibiotics, but TB is different.

People diagnosed with active TB disease generally have to take a combination of medications for 6 to 9 months. If you don’t complete the full treatment course, it’s highly likely the TB infection may come back. A returning infection can resist previous medications, so it’s often much more difficult to treat.

Your doctor may prescribe multiple medications because some TB strains are resistant to certain drug types. The most common combinations of medications for active TB disease include:

  • isoniazid
  • ethambutol (Myambutol)
  • pyrazinamide
  • rifampin (Rifadin, Rimactane)
  • rifapentine (Priftin)

These particular medications can affect your liver, so people taking TB medications should be aware of liver-injury symptoms, such as:

Notify your doctor immediately if you experience any of these symptoms. They’ll typically also check your liver with frequent blood tests while taking these medications.


A TB vaccine, called the bacillus Calmette-Guérin (BCG) vaccine, is mostly used in countries with a high prevalence of TB. This vaccine works better for children than for adults.

It’s not widely used in the United States because the risk of TB remains low. The vaccine can also interfere with TB skin tests and cause a false-positive result.

Treatment for tuberculosis can be successful, given a person takes all the medication as directed and has access to proper medical care.

If someone living with TB has other diseases, treating active TB may be more difficult. HIV, for example, affects the immune system and weakens the body’s ability to fight off TB and other infections.

Other infections, diseases, and health conditions can also complicate a TB infection, as can not having adequate access to medical care. Generally, early diagnosis and treatment, including a full course of antibiotics, offer the best chance for curing TB.

Even if the risk of TB is low where you live, it never hurts to be familiar with the things you can do to prevent contracting the TB bacteria or transferring the infection to others.

Preventing TB

The risk of being exposed to TB bacteria is very low in North America. That said, it’s still important to know how to prevent it in high-risk settings.

A few important steps you can take are:

  • connecting with a healthcare professional for testing if you believe you’ve been exposed to TB
  • getting tested for TB if you have HIV or any condition that increases your risk for infection
  • visiting a travel clinic or check with your doctor about testing before and after traveling to a country with a high TB rate
  • asking about your workplace infection prevention and control program and follow the precautions provided if your job carries a risk of exposure to TB
  • avoiding close or prolonged contact with someone who has active TB

Preventing transmission

According to the WHO, people with active TB can transfer the bacteria that causes the infection to between 10 and 15 people through close contact per year, if they don’t take precautions.

These steps can help prevent the transmission of TB:

  • Get tested if you have a higher risk of TB or think you may have been exposed.
  • If you test positive for latent or active TB, take all the medication prescribed.
  • If you’ve been diagnosed with active TB, avoid crowds and close contact with others until you’re no longer contagious.
  • Wear a mask if you have active TB and have to spend time around others.
  • Follow any other instructions provided by your doctor.

TB can be treated and cured, but it’s always best to start treatment as soon as possible.

If you believe you’ve been exposed, or have a higher risk of infection because of a medical condition or where you work or live, your doctor can offer more information and guidance on next steps.