Tuberculosis is a disease caused by a group of bacteria called Mycobacterium tuberculosis. It is also known as active tuberculosis or active TB. TB bacteria usually affect the lungs but can also affect other parts of the body such as the kidney, spine and brain. Some symptoms of TB disease are prolonged unexplained cough for longer than three weeks, weight loss, fever/chills, night sweats and coughing up blood. Sometimes TB disease has very mild symptoms and can be hard to diagnose. When a person with TB disease of the lungs or throat coughs, sneezes or talks, the TB bacteria travel from their lungs into the air. People who spend a fair amount of time in close contact with this person may breathe in these bacteria and become infected. People with TB disease must be isolated (until not infectious) and begin treatment which lasts a minimum of six months.

However, not everyone infected with TB bacteria develops TB disease. People who are not sick have what is called latent TB infection. People who have latent TB infection do not feel sick, do not have any symptoms and cannot spread TB to others. TB disease may develop after years of latent TB infection. Most people with latent TB infection can take medicine so that their risk of developing TB disease is reduced.

When the number of cases of a disease is less than five for one or more years, it is health unit policy to combine the data for multiple years. There were zero to six cases of TB diseases reported to Simcoe Muskoka District Health Unit each year between 2000 and 2008 for a total of 26 cases in this time period. The Simcoe Muskoka incidence rate is lower than the Ontario incidence rate:

The Simcoe Muskoka incidence rate varied between 0.2 - 1.4 cases per 100,000 population each year between 2000 and 2008 (Data Sources: iPHIS; Population Estimates and Projections 2000-08, Ontario MOHLTC, Provincial Health Planning Database (PHPDB) Extracted March 2009).
The Ontario incidence rate varied between 5.3 - 6.0 cases per 100,000 population each year between 2000 and 2004 (Data Sources: iPHIS; RDIS; Population Estimates and Projections 2000-08, Ontario MOHLTC, Provincial Health Planning Database (PHPDB) Extracted March 2009).

There are many factors that influence how many cases are reported to the health unit, as explained on the Infectious Diseases page.