TB is a bacterial infection that usually infects the lungs. It can be spread through close, prolonged or regular exposure to someone with active TB disease in the lungs or throat who is coughing or sneezing.
Screening for TB
Screening for TB infection is done by the TB skin test. A positive test shows that a person had the TB infection at some time in their life; it does not mean they have active TB. Over a lifetime, only about 10% of people with a positive skin test will develop active TB disease. Taking preventive drug treatment can reduce their chances of developing active TB disease later by as much as 90%. Those at a higher than average risk of getting TB include:
- People who have had close and prolonged contact with people with active TB
- Those from areas of the world where TB is common
- People with medical problems that reduce their ability to fight infection
- Drug users who use needles
- Those who are homeless or live in shelters and hostels
- Staff and residents of long term care facilities
- Hospitals and correctional centres
- Elderly people, especially those who lived through a time when TB was common
Latent TB Infection (LTBI) vs. Active Disease
Most people who breathe in the TB bacteria do not develop TB because their immune system fights it. Some bacteria may remain alive but not growing. This is called inactive or latent TB infection. Medicine is available to prevent TB from becoming active. Those with latent infection have no symptoms, have a normal chest x-ray, cannot spread TB germs and do not feel sick. They usually have a positive skin test and may develop active TB disease later in life.
TB bacteria become active if the body's immune system cannot stop them from growing. A physical examination, chest x-ray and sputum cultures are done to check for active disease. Symptoms include cough, night sweats, tiredness, chills, loss of appetite, weight loss and chest pain. Active TB can be treated and cured. Treatment usually means taking four or more different antibiotics for at least six months. A person may not be infectious as soon as two weeks but some people may be infectious for much longer. TB drugs are provided by the Ministry of Health and Long-Term Care and are free. Active disease must be reported to the public health department and will be thoroughly investigated to notify and follow up contacts.
Multi-Drug Resistant TB (MDR-TB)
Sometimes TB bacteria become resistant to the two most effective anti-TB drugs, Isoniazid (INH) and Rifampin (RMP). People with MDR-TB must be treated with special drugs and should be referred to a specialist familiar with drug resistant TB. Public health nurses can also give MDR-TB patients support, education and general follow up.
BCG is a vaccine against TB that is commonly used in countries with high TB rates. It is not recommended in Canada. People who have been vaccinated can still develop TB and should still be screened with a TB skin test and, if necessary, given a physical exam, chest x-ray and sputum test.