World Tuberculosis Day: In What Instances Does Latent TB Infection Become Active? Here’s What Experts Say

In some instances, tuberculosis bacteria can remain inactive for a lifetime without causing disease. But in people with a weak immune system, the bacteria become active, multiply and cause the disease

World Tuberculosis Day is observed every year on March 24 to commemorate the date in 1882 when Dr Robert Koch announced his discovery of Mycobacterium tuberculosis, the bacillus that causes tuberculosis. World Tuberculosis Day is dedicated to educating the public about the impact of tuberculosis around the world, and raising awareness to step up efforts to end the global tuberculosis epidemic. 

Tuberculosis is a serious illness caused by a bacterium called Mycobacterium tuberculosis, which most often affects the lungs, and spreads from person to person through the air. Only a small amount of the bacteria is enough to make a person infected. 

What is latent tuberculosis infection?

People who are infected with mycobacterium tuberculosis but do not become sick are said to have latent tuberculosis infection. In people with this condition, the bacteria can live in the body without making the host sick. The immune systems of people with latent TB infection are able to fight the bacteria to stop them from growing, and hence, show no symptoms, do not feel sick, and cannot spread tuberculosis infection to others, but may develop tuberculosis disease if they do not receive treatment for latent tuberculosis infection. 

How can latent tuberculosis infection become active?

In some instances, tuberculosis bacteria can remain inactive for a lifetime without causing disease. But in people with a weak immune system, the bacteria become active, multiply and cause tuberculosis disease.

Taking immunosuppressive medications can also make one’s immune system weak.

“Latent tuberculosis infection can become active when the immune system of an individual becomes weak, for example, due to conditions such as HIV (human immunodeficiency virus) infection, malnutrition, or diabetes. People who take immunosuppressive medications, such as those used to treat autoimmune diseases or organ transplant recipients, are also at higher risk of developing active tuberculosis disease,” Dr. Ambarish Joshi, Senior Consultant - Pulmonary & Sleep Medicine, Primus Super Speciality Hospital, New Delhi, tells ABP Live.

If the immune system is unable to contain the infection, the bacteria can spread within the lungs or other parts of the body, as a result of which symptoms can develop within a few weeks or months of the infection converting into active tuberculosis.

“People with latent TB do not have any symptoms and cannot spread TB. If they do not get treatment, however, they may develop active TB disease in the future, spread the disease to others, and feel quite ill. People with latent TB are not infectious to others. If the immune system fails to kill or contain the infection, it can spread within the lungs or other parts of the body and symptoms will develop within a few weeks or months of the bacteria converting into active TB,” Dr. Babina NM, Chief Medical officer, Jindal Naturecure Institute, Bangalore, tells ABP Live.

Some of the factors which can convert latent TB into active TB are age, malnutrition, smoking, and alcohol and drug use.

“People over the age of 65 years are at a higher risk of developing active tuberculosis disease. Poor nutrition can weaken the immune system and increase the risk of tuberculosis infection becoming active. Tobacco use can damage the lungs and weaken the immune system, increasing the risk of tuberculosis infection becoming active. Substance abuse can weaken the immune system and increase the risk of tuberculosis infection becoming active,” says Dr NM.

Of all the people exposed to Mycobacterium tuberculosis, approximately 30 per cent are thought to develop latent tuberculosis infection. The disease is diagnosed by a positive tuberculin skin test (TST). The process of latent tuberculosis infection becoming active is known as reactivation.

“After exposure to Mycobacterium tuberculosis, approximately 30 per cent of persons are thought to develop latent tuberculosis infection, as diagnosed based on a positive tuberculin skin test (TST). Around five to 10 percent of healthy (immunocompetent) persons with a positive TST will progress from LTBI to active tuberculosis disease (referred to as reactivation) in their lifetime. People who have diabetes, HIV, on immunosuppressive therapy, and chronic organ diseases are more prone to develop active tuberculosis from latent infection,” Dr. Arun Chowdary Kotaru, Consultant, Respiratory/ Pulmonology & Sleep Medicine at Artemis Hospitals Gurgaon, tells ABP Live.

Uncontrolled sugar levels can also cause the latent tuberculosis infection in a person to become active.

“If the immunity of a patient with latent tuberculosis infection goes down due to uncontrolled sugars or any immunosuppression caused by kidney, liver, or lung diseases, the infection can become active,” Dr. Arjun Khanna, Head, Department of Pulmonary Medicine, Amrita Hospital, Faridabad, tells ABP Live.

Therefore, people with latent tuberculosis infection should consume foods which ensure that they have a strong immune system.