Tuberculosis (TB) is an infectious disease most often affecting the lungs. It is caused by a bacteria called Mycobacterium tuberculosis.
The TB bacteria spread through the air when someone sick with TB coughs or sneezes. Tiny germ-containing droplets are expelled and may be inhaled by others. People with weakened immune systems have a high risk of getting infected.
TB has two potential phases – latent infection and active disease:
Latent TB: This is the inactive stage. Bacteria are present but dormant. The immune system limits them, so they cause no prominent symptoms and are not contagious. Still, without preventive treatment, latent TB may advance to active disease.
Active TB disease: Bacteria rapidly replicate, spread through the body, and damage tissue, typically the lungs. Symptoms manifest, and the illness may be transmitted to others. Without proper treatment, active TB may prove fatal.
Cough lasting over 3 weeks
Coughing up blood or sputum
Unexpected weight loss
Loss of appetite
Fever, chills, sweating at night
Sometimes TB escapes from the lungs to elsewhere, called extrapulmonary TB. Depending on the site impacted, symptoms may include:
Swollen neck lymph nodes
Children with TB show poor feeding and no weight gain. Whereas, older children may suffer from persistent fever.
Clinicians employ a combination of examination and tests to determine the presence of latent or active TB.
A. Initial assessment
A clinician inspects for swollen lymph nodes, palpation and auscultation of the chest, and elicits history about risk factors from the patient . Some common tests for the initial assessment of TB are:
Skin test: A substance, called tubulin, is injected under the skin. That part of the skin is checked for an immune reaction at the site within 72 hours. Swelling indicates the body has encountered TB. People vaccinated against TB give false positive results in this test. Some TB patients may give a negative so it is not a conclusive test.
Blood tests: Certain immune cells activate upon exposure to TB germs. A blood test of a person suspected of having TB is evaluated for the presence of such activated immune cells. A positive result means latent or active TB.
Acid fast bacilli test: The presence or absence of acid fast bacilli in the blood and sputum is indicative of TB.
Chest X-ray: This is an imaging test that shows abnormal spots in the lungs associated with active lung TB.
B. Confirming active TB
The above tests may not differentiate between latent and active TB. To confirm an active case, clinicians may analyze sputum, urine, spinal, or brain fluid samples for the presence of TB bacteria or substances that indicate the presence of TB bacteria. Imaging also assists in disease staging.
Understanding the unique traits of a patient’s TB strain enables precision treatment selection for the best outcome.
TB is curable, but medication regimens must be precisely tailored and diligently followed. Common medications include isoniazide, rifampin, rifabutin, rifapentine, pyrazinamide, and ethambutol.
Key factors determining the treatment are:
Active or latent disease
Site(s) of infection
Whether the strain is drug-resistant
During the latest phase of TB, the goal is eradicating bacteria before active illness develops. Options include long-term daily or weekly antibiotic dosing.
If the disease has reached the active stage, more aggressive therapy is employed to combat the infection for 6 months or longer:
Initial intensive 2-month phase
Continued 4-month maintenance phase
Adjustments are required if the TB strain is antibiotic-resistant. In some cases, removing severely damaged lung tissue via surgery assists recovery. Managing comorbidities also improves outcomes.
Tuberculosis is manageable with currently available standard-of-care diagnostic procedures and therapeutic strategies.. However, it is still a major healthcare burden in developing countries where more efforts are needed for its prevention, timely diagnosis, and effective treatment.