Can a patient with latent Tuberculosis (TB) spread TB to others?

Patients with Latent TB Cannot Spread TB to Others

Patients with latent tuberculosis infection (LTBI) cannot transmit TB to others. 1

Understanding Latent TB vs. Active TB

• Latent TB infection (LTBI) means a person is infected with Mycobacterium tuberculosis but does not currently have active disease. These patients are asymptomatic, have negative chest radiographs, and cannot transmit the infection to others. 1

• Only patients with active pulmonary or laryngeal TB can transmit the infection through aerosolized droplet nuclei produced by coughing, sneezing, speaking, or singing. 1

• The most infectious individuals are those who have not been treated for TB and have one or more of the following: pulmonary or laryngeal TB with cough, positive AFB sputum smear, or cavitation on chest radiograph. 1

Characteristics of Infectious TB

• Transmission of TB requires the following conditions:

  • Active disease in the lungs or larynx (not latent infection) 1
  • Presence of cough or undergoing cough-inducing procedures 1
  • Positive acid-fast bacilli (AFB) sputum smears 1
  • Inadequate or no treatment 1

• Extrapulmonary TB is generally not infectious unless there is concomitant pulmonary disease, disease in the respiratory tract/oral cavity, or an open abscess with high concentration of organisms. 1

Workplace and Isolation Guidelines for TB

• Healthcare workers with latent TB infection:

  • Should not be restricted from their usual work activities 1
  • Do not require isolation 1
  • Should receive counseling about the risk of developing active TB and be instructed to seek prompt evaluation if symptoms develop 1

• Only patients with active pulmonary or laryngeal TB require respiratory isolation until they are determined to be non-infectious (receiving effective therapy, showing clinical improvement, and having three consecutive negative sputum AFB smears collected on different days). 1

Risk of Progression from Latent to Active TB

• Approximately one-quarter of the world's population is latently infected with Mycobacterium tuberculosis. 2

• Certain individuals with LTBI have higher risk of progression to active (and potentially infectious) TB:

  • HIV-infected persons (35-162 cases per 1000 person-years) 1
  • Recent converters 1
  • Children under 5 years of age 1
  • Persons with fibrotic lesions on chest radiographs (2.0-13.6 cases per 1000 person-years) 1
  • Persons with certain medical conditions (diabetes, chronic renal failure, silicosis, immunosuppression) 1

Management Implications

• Contact investigations are necessary for active TB cases but not for latent TB cases, as LTBI is not transmissible. 1, 3

• Persons with LTBI should be evaluated for preventive treatment to reduce their risk of developing active TB, which would then pose a transmission risk to others. 1, 3

• The Centers for Disease Control and Prevention recommends that healthcare facilities have clear protocols for distinguishing between latent TB (non-infectious) and active TB (potentially infectious) to guide appropriate isolation and infection control measures. 1