Q. What is latent tuberculosis, and how is it different from active TB?

Doctor Answer is medically reviewed by SecondMedic medical review team.

Answered by Secondmedic Expert

Latent tuberculosis (LTBI) and active tuberculosis (TB) represent two stages of infection with the bacterium Mycobacterium tuberculosis.

1. Latent Tuberculosis (LTBI):
- In LTBI, a person is infected with the TB bacteria, but they do not exhibit any symptoms of active TB disease. The bacteria are alive but in a dormant state. Individuals with LTBI cannot spread the infection to others. LTBI is diagnosed through positive results in tests such as the tuberculin skin test (TST or Mantoux test) or interferon-gamma release assays (IGRAs). While LTBI does not cause illness, there is a risk that it can progress to active TB disease, especially if the person's immune system becomes compromised.

2. Active Tuberculosis (TB):
- Active TB occurs when the TB bacteria become active and multiply, leading to clinical symptoms and illness. Individuals with active TB can spread the infection to others through the release of infectious respiratory droplets. Common symptoms of active TB include a persistent cough, weight loss, fever, night sweats, and fatigue. Active TB is diagnosed through a combination of clinical evaluation, imaging studies (such as chest X-rays), and laboratory tests, including sputum cultures and nucleic acid amplification tests (NAATs).

The key differences between LTBI and active TB lie in the presence of symptoms, the ability to transmit the infection to others, and the need for treatment:

- Symptoms: LTBI is asymptomatic, whereas active TB manifests with clinical symptoms.

- Transmission: Individuals with LTBI are not infectious and cannot spread TB to others. In contrast, those with active TB can transmit the infection to others.

- Treatment: LTBI is typically treated to prevent the progression to active disease, especially in individuals with risk factors. Active TB requires more extensive and prolonged treatment with a combination of antibiotics.

Detection and treatment of LTBI are crucial components of TB control and prevention efforts, as they can help reduce the incidence of active TB cases and prevent the spread of the disease.