What is the difference between latent tuberculosis and active tuberculosis?

Latent tuberculosis (latent TB infection) differs from active tuberculosis (TB disease) in several key aspects regarding symptoms, transmissibility, and the need for treatment. In latent TB, TB bacteria are present in the body but are inactive, meaning the person does not exhibit symptoms and cannot transmit the infection to others. In active TB, the bacteria are active and multiplying, causing symptoms and enabling the person to transmit the infection to others.

Latent TB: Infection Without Disease

Latent TB occurs when a person is infected with Mycobacterium tuberculosis, but their immune system succeeds in containing the bacteria and preventing them from multiplying and spreading. In this state, the person does not experience any symptoms of the disease, does not feel sick, and cannot spread the bacteria to others through coughing, sneezing, or speaking [1]. However, there remains a risk that latent TB could develop into active TB in the future, especially if the person's immune system is weakened for any reason, such as HIV infection, diabetes, or the use of immunosuppressive medications [2].

Active TB: Symptoms and Transmission

Active TB occurs when TB bacteria actively multiply inside the body, leading to symptoms and making the person sick. Active TB primarily affects the lungs but may also affect other parts of the body such as the kidneys, spine, or brain [1]. General symptoms of active TB include fever, chills, night sweats, unexplained weight loss, loss of appetite, and weakness or fatigue [1]. If active TB is in the lungs, symptoms may include a cough lasting more than three weeks, chest pain, or coughing up blood or sputum [1]. People with active TB in the lungs or throat can spread bacteria to others through the air when coughing, sneezing, talking, or singing [2].

Diagnosis and Testing

To diagnose TB, skin or blood tests can be performed to detect the presence of TB bacteria in the body [1]. If the result of these tests is positive, it indicates the presence of bacteria, but does not determine whether it is latent or active. To determine if the bacteria are active, additional tests are required. For active TB in the lungs, these tests may include chest X-rays and sputum sample testing [1]. AFB (acid-fast bacilli) tests can help confirm an active TB diagnosis, especially following a positive TB screening test result [3]. Results for some of these tests, such as sputum culture, can take several weeks [3]. To learn more about TB in general, you can visit Tuberculosis: Symptoms, Diagnosis, and Treatment (Arabic).

Treatment and Prevention Options

Both latent and active TB require antibiotic treatment, but the duration and regimen of treatment differ. For latent TB, a person may need to take medication for three to nine months, depending on the treatment plan [1]. This treatment is essential to prevent latent TB from progressing to active TB in the future [2]. Active TB usually requires taking several types of antibiotics for four to nine months or longer to ensure all bacteria are eliminated and to prevent drug resistance [2]. It is crucial to follow the doctor's instructions and complete the entire course of treatment, even if the patient feels better, because stopping treatment early may lead to the return of the disease and the development of drug-resistant bacteria [1].

Medical references

• Tuberculosis
• About Active Tuberculosis Disease
• Acid-Fast Bacillus (AFB) Tests