Tuberculosis
Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis bacteria that most often affects the lungs and spreads through the air.
What tuberculosis is
Tuberculosis, or TB, is an infectious disease caused by Mycobacterium tuberculosis bacteria. It most often affects the lungs, but it can also involve the lymph nodes, bones, kidneys, brain, spine, or other parts of the body. TB has been treatable for decades, but it remains a major public-health challenge because it spreads through air and treatment takes time.
How TB spreads
TB spreads when someone with active TB disease in the lungs or throat releases bacteria into the air. People nearby may breathe in the bacteria. TB usually requires more sustained exposure than many common respiratory viruses, so household, workplace, healthcare, shelter, prison, or other close-contact settings can matter. It does not spread by sharing utensils or brief casual touch.
Latent infection and active disease
Many people who breathe in TB bacteria do not become sick right away. Their immune system can contain the bacteria, creating inactive or latent TB infection. People with latent TB do not feel sick and cannot spread TB, but the infection can become active later. Active TB disease causes illness and may be contagious when it affects the lungs or throat.
Symptoms
Active TB disease in the lungs can cause a cough lasting weeks, chest pain, coughing up blood or sputum, fever, night sweats, chills, weight loss, loss of appetite, and fatigue. TB outside the lungs can cause symptoms related to the affected body part, such as swollen lymph nodes, back pain, headache, or blood in the urine.
Testing and diagnosis
Testing can include a TB blood test or skin test to look for infection. If TB disease is possible, clinicians may use chest imaging, sputum tests, molecular tests, culture, and drug-susceptibility testing. Those follow-up tests matter because a positive infection test alone does not show whether TB is active, contagious, or drug resistant.
Treatment
TB treatment uses multiple medicines over weeks or months, depending on whether the person has latent TB infection, drug-susceptible active TB, or drug-resistant TB. Completing treatment exactly as prescribed is central. Stopping early or using the wrong medicines can allow bacteria to survive, come back, or become harder to treat.
Drug resistance
Drug-resistant TB develops when TB bacteria are not killed by standard medicines. Resistance can arise from incomplete or ineffective treatment, poor-quality medicines, delayed diagnosis, or transmission from someone who already has resistant TB. Drug-resistant TB usually requires longer, more complex, and more closely monitored care.
Why it matters
Tuberculosis matters because it combines individual illness with community risk. One missed case can expose many people, while one completed treatment plan can protect a household and stop transmission. TB control depends on trust, ventilation, testing access, contact investigation, medicine supply, and public-health follow-through.