Active tuberculosis (TB) disease can transmit from person to person, but latent TB infection is not contagious. Active TB typically transmits through droplets in the air.

The bacterium Mycobacterium tuberculosis causes TB. When active, it typically affects a person’s lungs but can also spread to other areas of the body, such as the spine or kidneys.

Experts divide TB into two categories: inactive — or latent — TB infection and active TB disease. An inactive infection will not cause any symptoms and will not transmit from person to person. Active TB disease causes symptoms, may transmit to others, and may be fatal without treatment.

This article reviews how TB transmits, incubation periods, whether a person needs to isolate, and more.

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TB transmits through the air only if a person has active TB disease, meaning they show signs of infection.

TB typically affects the lungs. It can transmit from one person to another when a person with active disease:

  • sneezes
  • coughs
  • talks
  • shouts
  • sings
  • blows out air

Once a person inhales the particles, the bacteria enter their lungs. They can also affect other areas of the body, including the kidneys, brain, or spine.

If TB spreads to the kidneys, spine, or brain, it is generally not transmissible to others. It is typically only infectious if it is in the throat or lungs.

How tuberculosis does not transmit

A person cannot transmit TB in the following ways:

  • using toilet seats
  • sharing cups
  • sharing or touching somebody else’s clothing
  • sharing eating utensils
  • handshakes
  • touching any other surface

Learn more about TB.

A 2018 review found that the average reported incubation ranges between several months and 2 years.

The Centers for Disease Control and Prevention (CDC) note that a person may develop an active TB infection within weeks of exposure, or it could take years before it develops into TB disease.

Others may never develop TB disease. When the condition develops, it is typically due to a weakened immune system.

A person with an inactive or latent TB infection does not need to isolate.

However, officials recommend isolation and taking safety precautions for people with active TB disease or those suspected of having TB. After treatment, or if tests rule out TB, they can typically return to their usual activities.

The CDC identifies two large groups of people at risk for TB. They include people recently exposed to TB infection and those with weakened immune systems.

People most at risk of active TB include:

  • people moving to or living in a country with high rates of TB
  • having regular close contact with a person with infectious TB disease
  • children under the age of 5 who have a positive TB test
  • people who work or live in high risk facilities, such as hospitals or shelters
  • groups with high rates of TB transmission, such as:
    • people living with HIV
    • people who use injection drugs
    • individuals experiencing housing insecurity or homelessness

In general, children and infants fall into the category of having a weaker immune system. Adults may have a weakened immune system due to underlying conditions, such as:

It may be possible to prevent latent TB infection from developing into TB disease.

A person with possible TB exposure should contact a primary care doctor or visit a health clinic. They can test for TB using either a skin or blood test. If they suspect TB disease, they may order additional testing, such as a chest X-ray or sputum sample.

A person known to have an inactive TB infection typically needs medication to prevent TB disease from developing later. Those with active TB disease will also require medication to treat the infection.

Other steps a person can take to reduce the risk of TB include:

  • spending time in well-ventilated areas if around somebody with active TB
  • avoiding close contact with a person with active TB
  • practicing good personal hygiene
  • asking their doctor about the Bacille Calmette-Guérin (BCG) vaccine for TB

People at risk may benefit from taking the BCG vaccination for TB. However, it is not in wide use in the United States due to low risk of exposure.

The CDC recommends its use for people working in hospitals or similar settings with possible exposure to drug-resistant strains of TB.

It may also benefit children who live with or have exposure to adults with active TB disease or ineffective treatment of the condition.

However, people with weakened immune systems or who are pregnant should not receive the vaccination.

Learn more about the BCG vaccine.

Symptoms of TB in the lungs can include:

If the infection spreads to other areas of the body, symptoms will vary based on what part is affected. Other possible symptoms of TB can include:

It is best for a person to contact a doctor if they have known TB exposure.

This may be due to traveling to another country with a high TB disease rate, working in a healthcare facility with possible exposure, or having close personal contact with those who have the disease.

Doctors can diagnose TB through either a skin test or blood test.

If a test shows TB infection, they may order an X-ray or sputum test to check for an active infection.

The two most common treatments for TB include the 4-month rifapentine-moxifloxacin TB treatment and the 6- or 9-month RIPE TB treatment.

A person can discuss the advantages and disadvantages of each treatment option with a doctor to determine what treatment may be best for them.

Here are some more common questions about TB.

Is it safe to be around someone with TB?

A person should use precautions when around someone with TB disease. This can include avoiding close contact and spending time in well-ventilated areas.

Can TB be cured?

There are various treatments for TB, which can last anywhere from 4–9 months to help resolve the condition. There are some drug-resistant strains, so a doctor will likely test for them before starting a treatment.

What happens if you have exposure to someone with TB?

A person should contact a doctor if they have known exposure to someone with active TB disease. As latent TB infection is not transmissible, a person does not need to take action if they come into contact with someone with the inactive infection.

Tuberculosis (TB) is transmissible when a person has active TB disease. This means they will have symptoms that can include coughing, fever, and other signs of being unwell. TB transmits when bacteria enter the air. A person then breathes in the particles, which can then enter the lungs.

A person should strongly consider contacting a doctor if they suspect they have had exposure to TB. A medical professional can order tests and provide treatment if they show either an active or inactive TB infection.