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Infectious Diseases


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What is tuberculosis?

Tuberculosis is a disease often called TB.  It is spread by bacteria (germs) that can float in the air.  TB spreads from person to person through the air only when someone who is sick with active TB disease in the lungs coughs, talks, sings or sneezes. 

TB is a complicated disease. Not everyone who becomes infected with TB becomes sick and develops TB disease.  When you are just infected, but not sick, you are not contagious.

Latent TB Infection

Most people who breathe in the TB germs are able to stop them from growing.  Most people's immune system traps the TB germs and keep them inactive.  This is called latent TB infection (LTBI).

People with LTBI do not feel sick and do not have any symptoms, but usually have a positive reaction to the tuberculin skin test.   People with LTBI cannot pass the germs to others.

There is treatment for latent TB infection to prevent TB disease.

Active TB Disease

TB germs become active when the body's immune system cannot stop the germs from growing. The active TB germs begin to grow and cause damage to the body.

The general symptoms of active TB Disease include:

  • New or worsening cough that lasts for more than 3 weeks or keeps getting worse
  • Feelings of tiredness or weakness
  • Unexplained weight loss
  • Fever
  • Chills
  • Night sweats
  • Other symptoms (based on where the TB germs are located in the body

If you think you may have TB, see your healthcare provider. TB treatment and medication are free in Ontario.  For more information or if you have any questions, call the Infectious Diseases Team at the Simcoe Muskoka District Health Unit 1-877-721-7520 ext. 8809. 

How soon do symptoms appear?

The highest risk of TB disease is within the first two years of becoming infected.

How is TB diagnosed?

Do not get tested if you have been told your test was positive in the past or if you have taken TB medicine.  Instead, speak to your health care provider. There are two ways to find out if you have TB infection:

  1. A skin test on your arm. The arm is looked at 2-3 days later by your health care provider.
  2. A blood test (IGRA).

If one of these tests come back positive, you may need more testing to rule out TB Disease. 

TB Disease Testing

  1. Chest X-ray
  2. Sputum tests
  3. Other tests, if needed

TB Infection & TB Disease
are not the same
It is important that you know the difference. 

TB Infection (Latent TB)

TB Disease (Active TB)

You are not contagious.

You are contagious if the TB germ is in your lungs. 

You have the germs in your body. Your body has trapped the TB germs so that they cannot continue to grow and multiply.

TB germs are multiplying and causing damage. TB usually causes disease in the lungs but can also affect other organs. 

You have a positive skin test. Your chest x-ray showed no TB Disease. You may develop TB Disease in the future.

You may have the following symptoms: weakness, fever, weight loss; cough, chest pain, coughing up blood when TB is in the lungs; pain if TB is in other parts of the body. 

TB infection can be treated with medication to prevent TB Disease from developing. 

TB Disease is treatable and curable as long as you take all your medication.
Early treatment prevents the spread of TB to others.


For data on the incidence of Tuberculosis in Simcoe Muskoka and Ontario, please visit the Tuberculosis page on the health unit’s HealthSTATS site

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