Infectious diseases are caused by the activity of one or more infectious agents. Ontario's Health Protection and Promotion Act states that certain infectious diseases or suspected occurrences of these diseases must be reported to local health units by health care providers, laboratories and administrators of institutions such as long-term care homes. Health units in turn must report these diseases, known as reportable diseases, to the Ministry of Health and Long-Term Care. These diseases are identified on Ontario's reportable diseases list.

The number of cases of disease reported to the health unit may not reflect the true number of cases in the community. In order for a disease to be reported, the person with the disease must seek medical help, a health care professional must order the diagnostic test, the test result must be positive and a health care professional must report the positive result. There are many factors that can influence each of these steps. These factors must be considered when interpreting the data.

This section of HealthSTATS provides information on the number of cases and incidence rates of reportable diseases in Simcoe Muskoka and Ontario. The source of the Simcoe Muskoka data is the provincial reportable disease database called iPHIS. The sources of the Ontario data are iPHIS (2005-08) and the reportable disease database that preceded iPHIS called RDIS (2000-2004).

Data are available on the following 15 reportable diseases in Simcoe Muskoka:

Information about the other reportable diseases is not currently available on HealthSTATS due to two possible reasons: there are relatively few cases of the disease (i.e. fewer than five per year for at least one year between 2000 and 2008); and/or the quality of the data in the database does not meet reporting standards. The latter reason applies to Hepatitis C and Hepatitis B. Measures are being taken to rectify the data quality issues.

Health units across Ontario maintain a constant surveillance of reportable diseases. This is necessary to analyse disease trends, identify outbreaks, implement prevention strategies and make recommendations for controlling the disease.