TB is caused by a specific bacterium that is easily spread between people. The bacteria travels through the air in droplets from a person with an active TB infection. The droplets are released with coughs, sneezes, or talking. The bacteria in the droplets can be breathed in by other people.

Pathway to the Lungs
Air pathway breathing
Bacteria is inhaled through the mouth and nose, and travels down into the lungs causing TB.
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Risk Factors

Babies, young children, and older adults are more likely to get TB when exposed.

Other things that may raise the risk of TB exposure are:

  • Close contact with a person with active TB
  • Living or traveling to an area where TB rates are high
  • Working in certain jobs, such as farming, funeral homes, and healthcare
  • Living or working in crowded, indoor conditions, such as prisons, hospitals, homeless shelters, or nursing homes

Things that may raise the risk of active TB are:

  • TB bacteria infection in the last two years
  • Chronic diseases that weaken the immune system, such as HIV infection
  • Taking medicine that weakens or suppresses the immune system, such as chemotherapy drugs or organ transplant anti-rejection medicine
  • Smoking or exposure to second hand smoke
  • Alcohol or substance use disorder



Active TB may cause:

  • Fever and chills
  • Night sweats
  • Weakness or fatigue
  • Weight loss
  • Lack of hunger
  • Pain in the chest
  • Severe cough that lasts more than 2 to 3 weeks
  • Coughing up blood and mucus


Active TB may be found during a routine check-up. The doctor will ask about symptoms and health history. You will also be asked about any TB exposure. A physical exam will be done.

These tests will be done to look for signs of infection:

  • Skin test
  • Blood tests

These tests may be done to rule out active TB:

  • Chest x-ray to look for changes caused by TB
  • Samples of sputum to look for the bacteria



The infection will need to be treated. This can be done with a combination of medicines. Treatment often lasts 6 months or longer. All the medicine must be finished to prevent drug-resistant TB.

Someone with active TB can easily spread the infection to others. This can be prevented by staying home and avoiding contact with others.


To lower the risk of TB:

  • Avoid contact with people who have active TB.
  • Avoid travel to areas with high rates of TB.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.