Tuberculosis

For most Canadians, the risk of developing tuberculosis (TB) is very low. Still, there are about 1,600 new cases of TB reported in Canada every year, so it is important to know the symptoms and how to minimize your risk.

Even though tuberculosis can be cured with antibiotics, it continues to be a major health problem. In 2010, approximately 1.4 million deaths related to TB were reported worldwide.

On this page:

• What is tuberculosis (TB)?
• How is it spread?
• Who's at risk?
• Symptoms
• Diagnosis
• Treatment
• For more information

What is tuberculosis (TB)?

TB is a serious disease that usually attacks the lungs, but can also affect other parts of the body, including the lymph nodes, kidneys, urinary tract, and bones.

TB infection

Most people who are exposed to TB bacteria do not develop TB disease. Sometimes, your immune system can kill the TB germs, but when this does not happen, the bacteria can remain alive but inactive in your body. This is called latent TB infection (also known as LTBI). If you have latent TB infection, you have no symptoms, are not sick, and present no risk of spreading the bacteria to others.

TB disease

TB infection can become TB disease (also known as active TB) if your 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 it spread?

TB is not as contagious as many other diseases (like the 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 (when coughing, sneezing, singing, playing a wind instrument or, to a lesser extent, talking).

To become infected, you usually have to be exposed often to someone with active TB disease. For example, spending several hours a day with a person with active TB disease would put you at risk for infection. You cannot become infected with TB by shaking hands, sitting on toilet seats or sharing dishes with someone who has TB.

Who's at risk?

HIV and AIDS, which weaken the immune system, are the most important risk factors for TB infection and TB disease. A person who has TB infection and HIV or AIDS is 50-170 times more likely to develop TB disease than someone who does not have HIV. For this reason, anyone who has HIV should be tested for TB.

Also, anyone with TB infection or disease should be tested for HIV for these reasons:

• to see if they need HIV treatment
• to help choose the best anti-TB drugs if they also have HIV infection

TB infection risk factors

In addition to persons with HIV and AIDS, certain population groups in Canada have an increased risk of TB infection. These groups include:

• those who have come into close contact with individuals with known or suspected TB disease
• people with a history of active TB, or an x-ray suggesting they had TB in the past but did not receive adequate treatment
• people living in Aboriginal communities with high rates of TB infection or disease
• the poor, especially the urban homeless
• residents of long-term care and correctional facilities
• people who work with any of the above groups (such as health care workers and correctional staff)

TB disease risk factors

The risk of TB infection developing into TB disease is greater for a person with a weakened immune system. Conditions/situations that weaken the immune system and increase the risk of TB disease include:

• HIV and AIDS
• organ transplants
• a type of lung disease called silicosis
• chronic kidney failure requiring dialysis
• cancer of the head and neck
• having been infected with TB within the past two years
• a chest x-ray showing signs of old TB
• treatment with steroids known as glucocorticoids
• treatment with tumour necrosis factor-alpha inhibitors (e.g., for auto-immune disorders such as rheumatoid arthritis)
• diabetes mellitus (all types)
• being underweight (for most people, this is a body mass index under 20)
• being under five years of age when first infected with TB
• cigarette smoking (one pack a day or more)

Symptoms

The symptoms of TB disease can include:

• a bad cough lasting longer than three weeks
• chest pain
• coughing up blood or sputum
• weakness or feeling very tired
• weight loss
• lack of appetite
• chills
• fever and night sweats

Diagnosis

TB infection  If you are not experiencing symptoms but suspect or know that you have been exposed to TB bacteria, you may be given a skin test to see if you have TB infection. For a skin test, a very small amount of non-infectious TB protein is injected under the surface of your skin. If you are infected with TB, a hard swelling usually develops at the injection site within 48 to 72 hours.

TB disease If you have TB infection, you may also need more tests such as a chest x-ray and collection of your sputum (phlegm) for laboratory testing to find out if you have TB disease.

Treatment

If tests show that you have TB infection and not TB disease, it is important to protect your immune system from becoming weak. TB drugs (antibiotics) may be prescribed and will help your immune system fight the TB germs and prevent TB disease. If you have TB infection, talk to your health care professional to find out if you need to take TB drugs. It is also important to find out if you have HIV. If you do, you need to take special precautions against TB infection and TB disease.

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 present a risk of spreading TB to others. They are also at greater risk for developing a strain of TB that is drug-resistant.