Tuberculosis
The Issue
For most Canadians, the risk of developing tuberculosis disease (TB) is very low. However, there are approximately 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.
Background
Tuberculosis has existed for centuries, and used to be called "consumption". It 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. Even though TB is completely curable with antibiotics, it continues to be a major health problem that kills almost two million people worldwide every year.
How TB is 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.
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.
Risk Factors for TB Infection and TB Disease
HIV/AIDS
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, all individuals who have HIV should be assessed for TB. Conversely, anyone with TB infection or disease should be tested for HIV for the following reasons:
- to see if they need to be treated for TB infection before it progresses to disease;
- to see if they would need HIV treatment; and
- to help choose the best anti-TB drugs if they also have HIV infection.
Other Risk Factors for TB Infection
In addition to persons with HIV or 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 active TB (e.g., family members sharing living spaces);
- 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; and
- residents of long-term care and correctional facilities.
People who work with any of these groups (e.g., health care workers, correctional staff) are also at greater risk of TB infection.
Other Risk Factors for TB Disease
The risk of TB infection developing into TB disease is greater for anyone with a weakened immune system. As noted earlier, HIV and AIDS are important risk factors for TB disease. Other conditions/situations that weaken the immune system include:
- organ transplants (because the patient is treated with immunity-suppressing drugs);
- a type of lung disease called silicosis;
- chronic kidney failure requiring dialysis;
- cancer of the head and neck;
- having been infected with TB bacteria 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 (TNF)-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 the TB bacteria; and
- cigarette smoking (one pack per day or more).
Symptoms of TB Disease
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
A skin test can determine whether you have TB infection. 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 (induration) usually develops at the injection site within 48 to 72 hours.
If the test shows that you do have TB infection, your health care provider may recommend antibiotic treatment to cure the infection before it develops into disease. Such treatment is especially important if you have an additional risk factor for developing TB disease (as noted above) or if you have been in recent contact with someone who has TB of the lungs or airways. You may also need additional tests or chest x-rays to determine whether you have 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 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.
Drug-resistant TB is harder and more expensive to cure. TB that is resistant to the two best "first-line" antibiotics used to treat TB disease is called multidrug-resistant TB (MDR-TB). If MDR-TB then becomes resistant to the best "second-line" antibiotics, it is called extensively drug-resistant TB (XDR-TB).
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.
The Government of Canada's Role
The Public Health Agency of Canada collects and analyzes data on all reported cases of TB in order to enhance Canada-wide TB prevention and control. The Public Health Agency also conducts national surveillance of TB drug resistance, co-publishes the Canadian Tuberculosis Standards for prevention and treatment, provides technical assistance (upon request) to provinces and territories to help prevent and control outbreaks, works with others in targeted research projects, and sponsors the Canadian Tuberculosis Committee.
In addition, Health Canada works with First Nations health authorities to reduce the incidence of TB in First Nations communities. In general, TB rates among First Nations peoples are five times higher than overall Canadian rates. For First Nations peoples living on reserve, TB rates are even higher, at eight to ten times the overall Canadian rate.
Need More Info?
Contact:
Tuberculosis Prevention and Control
Centre for Infectious Disease Prevention and Control
Public Health Agency Of Canada
100 Eglantine Driveway
Ottawa, ON K1A 0K9
Telephone: 613-941-0238
Fax: 613-946-3902
or visit the Public Health Agency of Canada's Web site for  Tuberculosis Prevention and Control
See also:
Also, see the following It's Your Health Articles:
For additional articles on health and safety issues go to the It's Your Health Web site.
You can also call toll free at 1-866-225-0709 or TTY at 1-800-267-1245*.
Updated: March 2007
Original: October 2002
© Her Majesty the Queen in Right of Canada, represented by the Minister of Health, 2007
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