Tuberculosis is a serious bacterial infection that spreads through the air

Tuberculosis (TB) is a disease caused by bacteria called Mycobacterium tuberculosis. When a person with TB coughs, sneezes, or speaks, they release tiny droplets containing the bacteria into the air. Other people breathe in these droplets and can become infected. TB most commonly affects the lungs, but it can also damage the kidneys, spine, brain, and other organs.

TB is not like a cold or flu that you catch and recover from in a week or two. It is a chronic infection, meaning it can last for months or years if left untreated. Some people develop active TB disease within weeks of infection. Others carry the bacteria in their body without ever getting sick — a condition called latent TB infection. Both forms are real medical conditions that doctors can identify and treat.

TB has existed for thousands of years and remains a leading infectious disease worldwide. In the United States, TB is less common than it was decades ago, but new cases are still reported every year. The disease is treatable with antibiotics, but only if a person knows they have it and receives proper medical care.

Key Takeaways

  • Tuberculosis is caused by bacteria that spread through the air when an infected person coughs or sneezes.
  • Active TB disease can damage the lungs and other organs and causes symptoms like cough, fever, and weight loss.
  • Latent TB infection means the bacteria are in your body but you have no symptoms and cannot spread the disease to others.
  • A skin test, blood test, or chest X-ray can show whether you have TB infection or active disease.
  • TB is curable with a course of antibiotics taken over several months, but treatment must be completed as prescribed.

How doctors tell the difference between latent and active TB

Not everyone infected with TB bacteria becomes sick. Your immune system may be strong enough to stop the bacteria from multiplying, keeping them dormant in your body. This is latent TB infection. You have no symptoms, you feel fine, and you cannot spread TB to other people. However, the bacteria are still alive, and there is a risk they could become active later in life, especially if your immune system weakens.

Active TB disease means the bacteria are multiplying and damaging your lungs or other organs. You develop symptoms and can spread the disease to others. Doctors use three main tests to figure out which type you have. A TB skin test (also called a Mantoux test) involves injecting a small amount of protein under your skin and checking for a reaction 48 to 72 hours later. A TB blood test measures your immune response to TB bacteria. A chest X-ray shows whether there is damage in your lungs that suggests active disease.

If you have latent TB, your skin or blood test will be positive, but your chest X-ray will look normal and you will have no symptoms. If you have active TB, your test results will be positive and your X-ray will show changes in your lungs, or you will have symptoms like a persistent cough, fever, night sweats, or weight loss.

Why TB counts as a disease and not just an infection

The word "infection" means bacteria or another germ has entered your body. The word "disease" means that infection is causing harm — damaging tissue, triggering symptoms, or making you sick. TB is both an infection and a disease because the bacteria do not just sit quietly in your body. They cause real damage.

In active TB, the bacteria destroy lung tissue, creating cavities (hollow spaces) that can be seen on an X-ray. This damage causes the symptoms people recognize: a cough that lasts more than three weeks, chest pain, coughing up blood, fever, chills, and night sweats. The bacteria can also spread to other organs and cause disease there. TB of the spine, for example, can cause severe back pain and permanent disability if untreated.

Even latent TB is classified as a disease state because it carries health risks. People with latent TB have a 5 to 10 percent chance that the bacteria will become active at some point in their life. The risk is higher for people with weakened immune systems, such as those with HIV, those taking immunosuppressive medications, or those who are very young or very old. This is why doctors treat latent TB with preventive antibiotics — to stop the disease from developing.

How TB spreads from person to person

TB spreads only through the air, not through touching, sharing food, or sharing utensils. When a person with active TB coughs, sneezes, speaks, or sings, they release respiratory droplets containing TB bacteria. These droplets are tiny enough to float in the air for hours in a poorly ventilated space. Another person breathes in these droplets and the bacteria settle in their lungs.

Not everyone exposed to TB will become infected. Whether you get infected depends on how much bacteria you breathed in, how long you were exposed, and how strong your immune system is. People who spend a lot of time in close contact with someone who has active TB — like family members or healthcare workers — have a higher risk of infection than someone who has brief contact.

Once the bacteria are in your lungs, your immune system begins to fight them. In some people, the immune system wins and clears the infection completely. In others, the immune system controls the bacteria but cannot eliminate them, leading to latent TB infection. In still others, the bacteria multiply and cause active disease.

What happens if TB is not treated

Untreated active TB can cause severe and permanent damage. The bacteria continue to destroy lung tissue, creating larger cavities and causing more bleeding. People may cough up blood or have difficulty breathing. The infection can spread to other parts of the body — the brain, kidneys, bones, and lymph nodes — causing disease in those organs as well.

TB meningitis, an infection of the membrane around the brain and spinal cord, is one of the most serious forms. It can cause permanent brain damage, paralysis, or death. TB of the bones and joints can cause chronic pain and disability. Without treatment, active TB disease is fatal in most cases.

People with untreated active TB also continue to spread the disease to others. A person with active TB can infect 10 to 15 other people over the course of a year if they are not treated. This is why public health authorities track TB cases and make sure people receive treatment.

How TB is treated and cured

TB is curable with antibiotics. The standard treatment for active TB disease involves taking four antibiotics together for two months, followed by two antibiotics for four more months. The exact medications and duration depend on the type of TB and whether the bacteria are resistant to certain drugs. It is critical to take all the medications exactly as prescribed and to complete the full course, even after you start feeling better.

If you stop taking antibiotics early, the bacteria can survive and become resistant to the drugs, making TB much harder to treat. Drug-resistant TB requires longer treatment with more medications and has a lower cure rate. This is why doctors and public health workers emphasize completing the full course of treatment.

For latent TB infection, doctors typically prescribe a single antibiotic taken daily for three to nine months, depending on which medication is used. This preventive treatment stops the bacteria from becoming active and developing into disease. People with latent TB who receive this treatment have a much lower risk of ever developing active TB disease.

Why TB is classified as a reportable disease

In the United States, TB is a reportable disease, meaning doctors and laboratories must report every confirmed case to the local health department. This is not a punishment — it is a public health measure designed to stop the spread of disease. When a case is reported, a public health worker contacts the person and helps them access treatment, tracks their progress, and identifies people who may have been exposed.

Public health workers also investigate where the person likely got infected and whether they may have exposed others. If someone with active TB worked in a school, healthcare facility, or other place where many people gather, the health department may recommend testing for people who were in close contact. This system has been in place for decades and has helped keep TB rates low in the United States.

Being reported does not mean your information is shared publicly or that you will face legal consequences. Health departments keep TB cases confidential and focus on getting people the treatment they need.

Frequently Asked Questions

Can you catch TB from someone who has latent TB?

No. People with latent TB infection have no symptoms and cannot spread the disease to others. Only people with active TB disease can spread TB through the air. This is why latent TB is not considered contagious.

Is TB the same as pneumonia?

TB and pneumonia are different diseases, though TB can cause pneumonia-like symptoms. Pneumonia is usually caused by different bacteria, viruses, or fungi and develops quickly. TB develops slowly over weeks or months. A chest X-ray and TB tests can tell the difference.

Can you get TB more than once?

Yes, though it is uncommon. If you have been treated for active TB and cured, you can still become infected again if you are exposed to TB bacteria. However, your immune system may recognize the bacteria and fight them off more effectively the second time.

What should I do if I think I have been exposed to TB?

Contact your doctor or local health department and tell them about the exposure. They can perform a TB test to see whether you have been infected. If you have latent TB, preventive antibiotics can stop it from becoming active disease.

Does TB only affect the lungs?

TB most commonly affects the lungs, but the bacteria can spread to almost any organ in the body. TB can cause disease in the bones, joints, kidneys, brain, and lymph nodes. These forms are less common but can be serious if not treated.