What is the difference between active and latent Tuberculosis (TB)?

From the Guidelines

The main difference between active and latent tuberculosis (TB) is that active TB is contagious and causes symptoms, while latent TB is non-contagious and asymptomatic. In active TB, the bacteria (Mycobacterium tuberculosis) are multiplying and causing illness, typically affecting the lungs with symptoms like persistent cough, chest pain, weight loss, fever, night sweats, and fatigue 1. People with active TB can spread the disease to others through airborne transmission when they cough, speak, or sneeze. Treatment for active TB typically involves a combination of antibiotics including isoniazid, rifampin, ethambutol, and pyrazinamide for 6-9 months.

In contrast, latent TB occurs when someone is infected with TB bacteria but the immune system has contained the infection, preventing illness and contagion 1. People with latent TB test positive on TB tests but have no symptoms and cannot spread the disease to others. However, latent TB can activate later, especially if the immune system weakens.

• Key characteristics of latent TB include:
  • Presence of immune responses to Mycobacterium tuberculosis infection without clinical evidence of active tuberculosis (TB)
  • No symptoms and not infectious
  • Risk of reactivation TB, which can be averted by preventive treatment
• Treatment for latent TB usually involves a single antibiotic like isoniazid for 6-9 months, rifampin for 4 months, or a combination of isoniazid and rifapentine for 3 months to prevent progression to active disease 1.

It is essential to identify individuals with latent TB who are at high risk of progression to active disease, as the potential benefits of treatment outweigh the risks of drug-related adverse events 1. The World Health Organization (WHO) guidelines recommend systematic testing and treatment of latent TB in high-risk individuals, including those living with HIV, adult and child contacts of pulmonary TB cases, and patients with certain medical conditions 1.

From the FDA Drug Label

Isoniazid is recommended for all forms of tuberculosis in which organisms are susceptible. However, active tuberculosis must be treated with multiple concomitant antituberculosis medications to prevent the emergence of drug resistance. Isoniazid is recommended as preventive therapy for the following groups...

The difference between active and latent Tuberculosis (TB) is that:

• Active TB requires treatment with multiple concomitant antituberculosis medications to prevent the emergence of drug resistance.
• Latent TB is treated with preventive therapy, such as isoniazid, to prevent the development of active TB. Key points about latent TB include:
• It is often identified through a positive tuberculin skin test
• Preventive therapy is recommended for certain groups, including those with HIV infection, close contacts of persons with newly diagnosed infectious tuberculosis, and recent converters 2

From the Research

Difference between Active and Latent Tuberculosis (TB)

• Active tuberculosis (TB) has a greater burden of TB bacilli than latent TB and acts as an infection source for contacts 3.
• Latent tuberculosis infection (LTBI) is the state in which humans are infected with Mycobacterium tuberculosis without any clinical symptoms, radiological abnormality, or microbiological evidence 3.
• The key difference between active and latent TB is the presence of clinical symptoms and the ability to transmit the disease, with active TB being contagious and latent TB not being contagious 3, 4.

Characteristics of Active and Latent TB

• Active TB is characterized by the presence of clinical symptoms, radiological abnormalities, and microbiological evidence of the disease 3, 4.
• Latent TB is characterized by the absence of clinical symptoms, radiological abnormalities, and microbiological evidence of the disease, but with a positive immune response to Mycobacterium tuberculosis 3, 5.
• C1q levels have been shown to be a potential biomarker for differentiating active and latent TB, with significantly elevated levels in active TB patients compared to latent TB patients 6.

Diagnosis and Treatment

• Diagnosis of latent TB is typically done through targeted testing of individuals from risk groups with the tuberculin skin test or an interferon-γ release assay 5.
• Treatment of latent TB usually involves preventive chemotherapy, which can effectively protect individuals at risk from the development of tuberculosis, although adherence to medication can be a challenge 7, 5.
• The treatment for active TB typically involves a combination of drugs, including isoniazid, rifampin, pyrazinamide, and ethambutol, with the goal of clearing the infection and preventing transmission 7.