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What is Latent Tuberculosis Infection or LTBI: Is it Dangerous, Treatment, Diagnosis

Tuberculosis (TB) is a common infection and most of us have heard of it. But how many are aware of latent tuberculosis infection or LTBI. Yes, this too is a potentially serious infection just that it is in the latent form, but can become active, if given an opportunity. So, what latent tuberculosis infection? Is it dangerous? Let us find facts related to latent tuberculosis infection and find answers to these questions.

What is Latent Tuberculosis Infection or LTBI

What is Latent Tuberculosis Infection?

Latent tuberculosis infection is caused by the bacteria, Mycobacterium tuberculosis. People infected with latent tuberculosis do not have an active tuberculosis disease. It is estimated that in the United States alone, nearly 15 to 20 million people have latent tuberculosis infection. Amongst these, only five to ten percent of people suffering from LTBI are at an actual risk of developing the active tuberculosis disease. Hence, it is important to understand what latent tuberculosis infection or LTBI is.

Many people assume that as the disease is latent or dormant in their bodies, they do not need to get treated. But that’s wrong. People having latent tuberculosis infection, once identified need to get the proper treatment to eliminate the tuberculosis infection.

Screening is usually recommended for high-risk people such as

The most common screening test for latent tuberculosis infection or LTBI is targeted tuberculin skin testing. Many new tests are also being developed. People suffering from latent tuberculosis infection are definitely at a higher risk of developing the active disease, and this, need to undergo treatment, regardless of their age.

To understand what latent tuberculosis infection or LTBI is, you need to know how the infection spread and immune response. Tuberculosis infection spreads from person to person through the air, when an infected person sneezes or coughs. Normally, these are following responses when your body is exposed to tuberculosis bacteria in the air

  • Your body may kill off the tuberculosis bacteria so that you will not be harmed in the present or in the future.
  • The tuberculosis bacteria may make you ill, resulting in active tuberculosis.
  • The tuberculosis bacteria enters your body and remains ‘asleep’ in the body, in the non-active or latent form. This is known as latent tuberculosis infection.
  • While tuberculosis generally affects the lungs, it can also affect other body parts such as the spine, bones, kidneys or even the brain.

Is Latent Tuberculosis Infection or LTBI Dangerous?

Is latent tuberculosis infection or LTBI dangerous? This is next question that comes to your mind. For this, you need to understand how latent tuberculosis infection affect health and if can cause any harm.

People having latent tuberculosis infection do not realize that they have the bacteria as they do not feel sick and neither do they show any symptoms of the disease. They are infected with the bacteria but do not have active disease. However, the only sign of them suffering from tuberculosis infection is a positive result of the tuberculin skin test or the tuberculosis blood test. It is important to note that people having latent tuberculosis infection are not infectious and cannot spread this infection to others through coughing or sneezing.

The main reason why latent tuberculosis infection or LTBI is dangerous is that without any treatment, nearly ten percent of all infected people will go on to develop active tuberculosis disease at some point in their lives. There is greater risk during the first two years of infection.

Some people with greater risk of developing an active form include

People who have a weakened immune system, particularly those who are infected with the HIV virus. In HIV-infected people, TB remains the leading cause of death globally.

  1. Small children, or the elderly
  2. People suffering from diabetes

Latent tuberculosis infection is dangerous also because, people who get infected by extensively drug-resistant tuberculosis end up having that the same form of tuberculosis, if it becomes active. This form is potentially dangerous than others as it is resistant to several drugs and treatment becomes a challenge.

Differences Between Active and Latent Tuberculosis Infection

While latent tuberculosis infection can be treated to prevent it from becoming active tuberculosis, many people usually do not realize that they have the latent tuberculosis bacteria and continue to go about their lives as normal. As latent tuberculosis infection is dangerous, it is important to know the differences and get timely screening done.

Let us look at the main differences between latent and active tuberculosis infection.

Latent Tuberculosis Infection

  • The tuberculosis bacteria remains asleep in the body
  • A person does not display any symptoms and continues to feel perfectly normal and well.
  • It is not possible to pass on the tuberculosis bacteria to others
  • Latent tuberculosis infection can only be detected by a tuberculosis skin test or a blood test.
  • Latent tuberculosis infection can be treated with one or two medicines during a period of three to six months.

Active Tuberculosis Infection

  • The tuberculosis bacteria are active inside the body and make the person ill.
  • Tuberculosis symptoms will be present and the person will feel unwell.
  • It is possible to pass on the tuberculosis bacteria to others if the disease is present in your lungs.
  • The disease shows up on a chest x-ray if tuberculosis is present in the lungs.
  • Active tuberculosis needs to be treated over a period of at least six months, with four or more medicines.

How to Know That Latent Tuberculosis Infection is Becoming Active?

Once a person has been diagnosed with latent tuberculosis infection, they need to remain alert for signs and symptoms if the latent infection is now transforming to an active disease. Even after completing the full medication course for treating latent tuberculosis infection or LTBI, there is a risk of developing an active infection.
The symptoms of active tuberculosis may remain mild for many months, causing delay in treatment and spread of infection to others. Hence, any one with latent tuberculosis infection or LTBI should watch out for these symptoms, to prevent it from taking a dangerous turn.

Tuberculosis can affect the lungs, spine, bones, joints, brain, kidneys, or other organs and areas too. Ignoring the symptoms that indicate a latent infection is becoming active, may result in eye damage, lung damage, organ damage, and even death in severe cases of the disease.

Therefore, even without a cough or flu-like symptoms, latent tuberculosis infection may still have converted into active tuberculosis. Symptoms when tuberculosis affects other parts of the body include:

Therefore, it is very important to get proper and timely treatment if you suspect any of the symptoms related to tuberculosis.

When Does Latent Tuberculosis Infection Get Activated?

Here are the conditions when latent tuberculosis infection or LTBI can become active and prove to be dangerous.

  • Immune system disorders, such as AIDS, or any disease whose treatment impacts the immune system, use of systemic steroids in asthma, or Humira/Orencia in rheumatoid arthritis, or chemotherapy in cancer.
  • Malnutrition, prolonged illness or an injury to the digestive system. A prolonged period of not eating or incidences such as a famine, war conditions, etc.
  • Aging leading to the degradation of the immune system
  • Latent tuberculosis infection is more likely to become active in elderly patients or very young patients.
  • Systemic diseases such as diabetes, cancers, end-stage renal disease, bypass, or long-term use of steroids.
  • People using illegal drugs

Latent tuberculosis infection can be dangerous in people who were not treated for tuberculosis properly in the past, or who did not complete the prescribed regimen for tuberculosis treatment.

Diagnosis of Latent Tuberculosis Infection or LTBI

There are generally two common tests that are used to diagnose latent tuberculosis infection. These are the tuberculin skin tests and the Interferon-gamma test (IFN-y) test.

The tuberculin skin test also includes:

  • Heaf test – this was discontinued in 2005 due to the high cost of the process.
  • Mantoux test
  • There are also three different types of IFN-y tests available.
  • QuantiFERON-TB Gold
  • QuantiFERON-TB Gold In-Tube

Treatment of Latent Tuberculosis Infection or LTBI

Treatment of latent tuberculosis infection or LTBI revolves around firstly controlling the infection with medicines to prevent it from becoming active.

While it is necessary to follow the prescribed medicines and recommended dose, the risk of tuberculosis infection remains high. This is one of the main reasons what latent tuberculosis infection is dangerous. Even after complete treatment, the symptoms may subside but it may not be known whether the infection is completely gone or has moved to the latent state. Therefore, patients having latent tuberculosis infection need to keep a careful watch on the signs and symptoms of their disease becoming active.

Maintaining a healthy lifestyle and taking care of oneself goes a long way in ensuring that the latent tuberculosis infection does not become active. Getting regular screenings done, following up for tuberculosis treatment and treating any conditions, which increase the risk of tuberculosis infection are necessary.


  1. World Health Organization (WHO) – Latent Tuberculosis Infection: https://www.who.int/tb/areas-of-work/preventive-care/ltbi_faqs/en/
  2. Mayo Clinic – Tuberculosis (TB) – Symptoms and Causes: https://www.mayoclinic.org/diseases-conditions/tuberculosis/symptoms-causes/syc-20351250

Also Read:

Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 2, 2023

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