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Reportable
Disease Information
System - Data Sources
Data Source
The Reportable Disease Information System (RDIS) is used to assist health departments with the case management, reporting and surveillance of reportable diseases within their jurisdiction. The health unit must report all confirmed cases of disease to the Public Health Branch of the Ontario Ministry of Health. RDIS records are transmitted to the Ministry on a weekly basis.
All reportable disease data presented in the health status report was generated from RDIS prior to December, 1999.
Data Limitations
Reporting delays may affect the number of cases of disease represented in this report and therefore the data can be used as an estimate only. This may be a particular problem for AIDS and HIV since the Laboratory Centre for Disease Control in Ottawa suggests that correcting for delays in reporting adds 30% more AIDS cases to the Canadian total and approximately 15% of all cases never get reported. Due to these reporting delays, data for 1998 was not included in this report.
The influenza case definition changed in 1996 and now excludes those that are epidemiologically linked to confirmed cases. Therefore, comparisons before and after 1996 should be interpreted cautiously.
The measles case definition also changed in 1996. It now includes the RDIS item "indigenous/imported" to help determine whether infection was acquired within Ontario or out-of-province. This type of information may not be available for cases diagnosed prior to 1996.
As with any reporting system, data collection and data entry methods vary, depending on the investigators and data entry persons. Standardized procedures are required to ensure that data are valid and reliable. Future data audits will improve the quality of the data.
Data on all nationally notifiable diseases, including enteric, foodborne, and waterborne diseases, are reported to provincial and territorial health deparments on confirmation of diagnosis. These are forwarded to the Laboratory Centre of Disease Control of Health Canada, where national Statistics are collated. These data are subject to a number of potential biases and inconsistnecies relating to local or provincial/territorial testing andreporting practices.
Only a small fraction of cases of enteric, foodborne, and waterborne illnesses are thought to result in reports. Any comparisons of reporting trends between provinces/territories and age groups should thus be interpreted with caution.
Each public health unit is responsible for collecting case information on reportable communicable diseases. This information is summarised for provincial and national surveillance.
The most common source of case identification is through laboratory notification of confirmed test results (serology, microbiology cultures, etc.). Physicians are required to report cases that fulfil laboratory or clinical case definitions.
There may be considerable under-reporting of actual cases for some diseases in RDIS. For instance, when a infected person has mild clinical symptoms they may not seek medical care and/or laboratory testing may not be performed.
Comparisons with Ontario rates are possible.
RDIS became operational in 1990; there are data integrity concerns for some areas and diseases in this year.