Is Tuberculosis (TB) Contagious?

Tuberculosis (TB) is an infectious disease caused Mycobacterium tuberculosis bacteria that usually affects the lungs. It is not common in the U.S., but it is still a leading cause of death in other parts of the world.

There are two TB-related conditions: 

• Latent TB infection
  • The body is able to fight the bacteria
  • The patient has no symptoms
  • TB cannot be spread to others in this stage
  • Will usually have a positive TB skin test reaction or positive TB blood test 
  • May develop TB disease if treatment is not received for latent TB infection
• TB disease
  • Patients are sick and have symptoms
  • Patients are contagious and the bacteria can be spread to others from the infected patient
  • The risk of developing TB disease is higher in people who have weakened immune systems

Symptoms of active tuberculosis disease include:

• Persistent cough that lasts 3 weeks or more
• Coughing up blood or sputum 
• Fever
• Chills
• Weakness 
• Fatigue
• Loss of appetite 
• Sweating at night
• Weight loss without trying 
• Chest pain

Tuberculosis is caused by the Mycobacterium tuberculosis bacterium. The bacteria are spread through respiratory droplets propelled into the air when an infected person coughs, sneezes, or even speaks.

Less commonly, tuberculosis may be spread by eating or drinking something infected with tuberculosis, such as unpasteurized milk from an animal with TB. 

Risk factors for developing tuberculosis include: 

• Known exposure to someone with active TB
• Birth or extended stay in a part of the world where TB is common
• Being a health care or laboratory worker who has contact with patients with active TB disease
• Taking medications that weaken the immune system, such as steroids or medications for rheumatoid arthritis
• HIV infection

Tuberculosis is highly contagious. The bacteria that cause TB are spread through respiratory droplets propelled into the air when an infected person coughs, sneezes, sings, or even speaks and another person inhales the airborne bacteria. 

People with latent TB infection who have no symptoms are not contagious, but if they reach the point where their body can no longer fight the infection and they develop active tuberculosis, they will become contagious. 

In addition, the Mycobacterium tuberculosis bacteria can survive in a person for some time after they have died, and anyone around the deceased, including physicians who perform autopsies, must be careful. 

Tuberculosis is diagnosed with the following tests:

• Tuberculin skin test, sometimes also called a purified protein derivative test (PPD)
• Consists of a shot in the arm containing tiny pieces of dead TB bacteria 

Two to three days later, the spot where the shot was administered is examined to see for evidence of a skin reaction (redness or swelling) and the extent of the reaction

• Skin tests are usually positive within 4 to 10 weeks after exposure 
• Blood test (interferon-gamma release assays [IGRAs])
  • Blood tests are available in many areas, but not everywhere

Latent tuberculosis infection is diagnosed with a positive skin test or blood test, followed by a physical examination and imaging such as a chest X-ray to make sure the TB is not active and causing disease.

Tuberculosis can be cured; however, the treatment regimens last for months and it is important for patients to take all medicines for the duration they are prescribed, exactly as prescribed.

If patients stop taking medications before the prescribed course is finished, or they do not take the medications as directed, they can become sick again and they may be resistant to the initial medications. 

• Drug-resistant TB is more difficult and more expensive to treat. 
• Untreated tuberculosis can be deadly. 

Treatment for latent tuberculosis infection usually lasts three months or longer and includes: 

There are several different drug regimens: 

• Rifampin daily for four months
• Isoniazid plus rifampin daily for three months
• Isoniazid plus rifapentine weekly for three months (usually given weekly by a trained health care worker)
• An alternative is isoniazid daily for six or nine months for people who cannot take rifampin or rifapentine
• Avoid alcohol and acetaminophen (Tylenol), both of which make the liver work harder, and may increase the risk of liver injury from TB medications
• People treated for latent TB infection are usually monitored once a month by a doctor to check for signs of medication toxicity, such as liver damage 

Treatment for active tuberculosis disease usually lasts 6 to 9 months and includes: 

• First-line anti-TB agents that form the core of treatment regimens are:
  • Isoniazid 
  • Rifampin 
  • Ethambutol 
  • Pyrazinamide 
• Regimens for treating TB disease have an intensive phase of 2 months, followed by a continuation phase of either 4 or 7 months (total of 6 to 9 months for treatment)

Untreated tuberculosis can be fatal. Complications of tuberculosis include: 

• Liver damage
• Kidney problems
• Joint damage from tuberculous arthritis
• Back pain and stiffness
• Meningitis 
• Heart problems (cardiac tamponade)