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What is Tuberculosis?

TB (tuberculosis) is a serious bacterial illness caused by Mycobacterium tuberculosis, that most commonly affects the lungs, but can involve any major organ system. Not everyone with TB becomes sick. As a result, two TB-related conditions exist: Latent TB Infection (LTBI) and TB disease (or active TB).

How do you become infected with TB?

TB bacteria are sprayed into the air through tiny moisture droplets when someone with active TB disease of the lung or throat laughs, coughs, sneezes, speaks, or sings. If someone else inhales these infectious droplets, the bacteria can settle in the lungs where they begin to multiply. They can move to other parts of the body, such as kidney, spine, and brain.

Latent TB Infection vs. TB Disease:

  • Latent TB Infection:  After exposure and inhalation, TB bacteria increase in number and spread out from the lungs. In healthy individuals, the immune system recognizes the infection and mounts a response to prevent this infection from making them sick. This is called LTBI. Many individuals who have LTBI never develop TB Disease. In these individuals, the bacteria remain inactive for lifetime. However, in some individuals, the bacteria become active, multiply, and cause TB Disease. Latent TB can transition to active TB Disease within a few weeks after exposure, to months, or even years later. This occurs in roughly 5 - 10% of infected individuals.
  • TB Disease: Occurs when TB becomes active and the immune system can’t stop the bacteria from growing and multiplying. Active TB is called TB Disease. These individuals are sick and experience a variety of symptoms. They can also spread the bacteria to other people, often those they spend time with every day such as family members, friends, coworkers and classmates.

Symptoms and Characteristics:

Laten TB:

  • No symptoms/does not feel sick
  • Can NOT spread TB
  • Have a POSITIVE test with no evidence of active disease on chest x-ray or sputum culture
  • At risk for developing TB Disease, if not treated

TB Disease:

  • Symptoms: bad cough > 3 weeks or longer, fatigue/weakness, fever, night sweats, weight loss/loss of appetite, coughing up blood or sputum, pain in chest
  • Can spread TB to others
  • Have a POSITIVE test and other positive findings on additional studies like chest x-ray and sputum culture

Who is at particular risk of TB infection?

For many reasons, some groups of people are at higher risk to get active TB disease. Risk factors include:

  • Close contact with those known to be infectious with TB disease
  • Originating from countries with high TB rates
  • Medical conditions that make the body less able to protect itself from disease (for example: Diabetes, low body weight, substance abuse, HIV infection) and those taking medications that inhibit the immune system (for example: long term corticosteroids, medications to treat RA, Crohn’s, cancer, etc.)
  • Living in overcrowded spaces or homeless shelters
  • Individuals who don't receive regular health care
  • Individuals who work or are residents of long-term care facilities such as prisons, nursing homes, and hospitals.

How do you check for TB infection?

There are two tests that can be used to help detect TB infection: TB blood test or TB skin test (TST).

  • Blood Test: measures how a person’s immune system reacts to the germs that cause TB. The blood test is not affected by previous vaccination with BCG.
  • TB Skin test (also called PPD, Mantoux Tuberculin Skin Test, or TST): a small needle is used to put some testing material, called tuberculin, under the skin in the lower forearm. In 2 – 3 days, you return to a health care provider to check to see if there has been a reaction to the test.

What does a positive result mean?

A positive test indicates a possible past infection with TB, but not necessarily active TB disease. A chest x-ray and possibly a sputum culture will then be completed to determine if active lung disease is present.

  • If the chest x-ray is normal, that means that the TB bacteria is not actively causing disease and the person is not infectious to other people at this time. That is considered a latent TB infection (LTBI).
  • If the chest x-ray or sputum culture is abnormal, this is called TB Disease and the individual is infectious and can actively spread the bacteria to others. This requires treatment by the local State Department of Health and TB Specialist. Other tests may be done if TB disease is suspected to be present in other parts of the body.

What about BCG vaccination?

BCG is given in some countries, but not generally in the United States. It is administered to improve the body's immune response to TB exposure. In individuals who have received a BCG vaccine, testing with the blood test is preferred, as this method is NOT affected by prior BCG vaccinations

Medication Treatment Details:

Treatment depends on the diagnosis. Treating LTBI greatly reduces the risk of the infection progressing to active tuberculosis later in life. While undergoing any treatment for TB (either LTBI or TB disease), it is important to avoid drinking alcohol and taking acetaminophen (Tylenol). Both substances can make the liver work harder, potentially increasing the risk of liver injury from the medication(s).

  • Anyone with TB Disease is treated by the local State Department of Health and TB Specialist.
  • Latent tuberculosis is treated with medications that kill the dormant bacteria. There are a variety of medications and dosing options that can be used to treat LTBI. The course is typically chosen on an individual basis, and based on multiple factors including medical history, other medications used by the patient, desired length of treatment, etc.

Adverse Drug Reactions:

Any reactions that may be possibly related to the use of these medications should be reported immediately to a health care provider. These include:

  • Unexplained loss of appetite, nausea or vomiting, dark urine (color of coffee or cola), or yellowing of skin
  • Persistent aches or tingling of hands or feet
  • Persistent weakness, fatigue, fever, or abdominal tenderness
  • Easy bruising or bleeding
  • Blurred vision or decreased visual acuity
  • Rash, fever, head/body aches or dizziness

Subsequent Care:

  • There is no definitive way to determine whether LTBI treatment has been effective in eliminating the infection. LTBI treatment prevents up to 90 percent of subsequent TB disease.
  • Patients with documented positive TST should never have repeat TST; once the test is positive, it generally remains positive.
  • In general, individuals with ongoing potential TB exposure who have a history of a positive test for LTBI and have completed a course of LTBI treatment should have a new baseline chest radiograph performed.


In an emergency go to Mount Nittany Medical Center or call 911 for an ambulance.

Test Results and Advice Nurse

Send a secure message to the advice nurse via myUHS or call 814-865-4UHS (4847) (Press 3). 


Schedule an appointment online or by calling the UHS.  

This content is reviewed periodically and is subject to change as new health information becomes available. This information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.

Approved by the UHS Patient Education Committee Revised 12/2022

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Tuberculosis: Latent TB Infection and TB Disease


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