Infectious diseases & vaccines Infectious diseases Tuberculosis (TB)

Tuberculosis (TB)

What is TB infection and TB disease?

Most people who are exposed to TB bacteria do not develop TB disease. In some cases, the person's immune system is able to kill the TB germs. When this does not happen, the bacteria can remain alive but inactive in the body, and this is called TB infection. A person with TB infection has no symptoms, is not sick and poses no risk of spreading the bacteria.

TB infection can become TB disease if the infected person's immune system cannot stop the TB bacteria from growing. The risk of developing TB disease is highest in the first two years after being infected. About 10% of infected people will develop TB disease at some point in their lives.

How is TB spread?

TB is not as contagious as many other diseases, such as influenza (flu) or chicken pox. Tuberculosis bacteria, called Mycobacterium tuberculosis, are spread through the air when someone with active TB disease of the lungs or airways exhales (e.g., coughing, sneezing, singing, playing a wind instrument or, to a lesser extent, talking). To become infected, a person usually has to have frequent exposure to someone with active TB. For example, spending several hours a day with a person with active TB would put you at risk of infection.

You cannot become infected with TB by shaking hands, sitting on toilet seats or sharing dishes with someone who has TB.


The symptoms of TB disease in the lungs can include a bad cough lasting longer than three weeks, pain in the chest, coughing up blood or sputum, weakness or feeling very tired, weight loss, lack of appetite, chills, fever and night sweats.

Diagnosis and treatment

TB is diagnosed by your health care provider.

Anyone with TB disease must take antibiotics for at least six months to kill all of the TB bacteria. People who do not finish a full course of antibiotic treatment may continue to pose a risk of spreading TB to others. They are also at greater risk for developing a strain of TB that is drug-resistant.

Minimizing your risks

If you belong to one of the groups at higher risk and suspect that you may have been exposed to TB bacteria, or if you are experiencing any of the symptoms of TB, you should see your health care provider.

If you are diagnosed with TB, it is very important to take the full course of antibiotics prescribed for you. This will help protect others and will also reduce your risk of developing a strain of drug-resistant TB.


Where to find more information

For more information about TB, download our brochure or follow the links below. TB brochure


Health Canada: It's your health - Tuberculosis (TB)

Ontario Public Health Standards - TB Prevention and Control

Public Health Canada - TB Prevention and Control

Public Health Canada - TB Fact Sheets

The Lung Association of Ontario - Lung Health

The Lung Association of Ontario - TB Info

Tuberculosis Screening in LTC Homes and Retirement Homes

World Health Organization - Tuberculosis (TB)