Currently undergoing revision

• The incidence rate is the total number of cases of selected enteric diseases relative to the total population (per 100,000).
• Age-specific incidence rates are the annual number of new cases of selected enteric diseases in a given age group per 100,000 population in that age group.
• Age-standardized incidence rate (SRATE): the number of new cases of selected enteric diseases that would occur in the population if it had the same age distribution as the 1991 Canadian population.
• Standardized incidence ratio (SIR): the ratio of observed new cases of selected enteric diseases to the number expected if the population had the same age-specific incidence rates as Ontario.

• Incidence of Campylobacter
• Incidence of Salmonella
• Incidence of Verotoxigenic Escherichia coli
• Incidence of Hepatitis A
• Incidence of Shigella
• Incidence of Typhoid
• Incidence of Paratyphoid
• Incidence of Amebiasis
• Incidence of Yersiniosis
• Incidence of Giardiasis
• Incidence of Cryptosporidiosis
• Incidence of Cyclosporiasis
• Incidence of Listeriosis  

Corresponding Mandatory Objectives
http://www.health.gov.on.ca/english/providers/pub/pubhealth/manprog/manprog.html

• To improve the health of the population by reducing the incidence of food-borne illness.
• To reduce the incidence of water-borne illness in the population.

Corresponding Outcomes from the Draft Ontario Public Health Standards (OPHS)
http://www.health.gov.on.ca/english/providers/pub/pubhealth/manprog/manprog.html

• There is reduced incidence of food-borne illness.
• There is reduced incidence of adverse events related to unsafe drinking water. 

Comparable health indicators: (Select “View” under latest issue then “Data tables”)
http://www.statcan.ca/bsolc/english/bsolc?catno=82-401-XIE 

• Incidence rate for Verotoxogenic E. coli

Suggested citation (see Data Citation Notes): Population Estimates [years]*, Provincial Health Planning Database (PHPDB) Extracted: [date], Ontario MOHLTC

* Note: Use the total years of the estimates, including the most recent year, even if not all were used in the analysis. The years used in the analysis should be included in the report itself.

  
Alternative Data Sources

Analysis Check List

• For iPHIS:
• To obtain an estimate of incidence, ensure that the "diagnosing health unit" is the health unit of interest.
• To include only cases (and not case contacts or reports that were investigated and subsequently found not to be cases): current diagnosis status classification = ‘confirmed'.
• Be aware that some diseases can occur more than once within the same person.

Method of Calculation
 

 
Basic Categories

• 5 year age groups for age-specific rates
• Sex: male, female
• Geographic areas: public health unit

  
Indicator Comments

• The peak incidence of enteric diseases is typically highest among children under the age of 4.
• Each health unit utilizes the centralized provincial reporting system, the Integrated Public Health Information System (iPHIS) which is used to collect reportable disease data. Provincial summaries are compiled by the Ontario Ministry of Health and Long Term Care's Infectious Diseases Branch, which allows for comparisons with Ontario rates. Comparisons with other health units can be problematic however, because of inconsistencies across health units.6 Some cases may also be double-counted among people who move or cross various health unit boundaries.
• iPHIS was implemented in every Ontario health unit in 2005.
• There were some issues around data integrity when the previous reporting system, the Reportable Disease Information System (RDIS) was first implemented in 1990. For some diseases, case definitions have changed over time. These data quality issues remain relevant, as RDIS cases were migrated into iPHIS. Refer to Resources: Canadian and Ontario Case Definitions for Infectious Diseases.
• There may be considerable under-reporting of actual cases for some diseases in iPHIS. For instance, when an infected person has mild clinical symptoms they may not seek medical care and/or laboratory testing may not be performed.
• To best understand mortality or disease trends in a population, it is important to determine crude rates, age-specific rates and age-standardized rates (SRATES) or ratios (SMRs, SIRs). The crude death (or disease) rate is the number of deaths (or disease cases) divided by the number of people in the population. This rate depicts the “true” picture of death /disease in a community although it is greatly influenced by the age structure of the population. An older population would likely have a higher crude death rate whereas a younger population may have a higher crude birth rate. Age-specific rates can best describe the “true” death /disease pattern of a community and allow comparison of populations that have different age structures.
• Since many age-specific rates are cumbersome to present, age standardized rates have the advantage of providing a single summary number that allows different populations to be compared; however, they present an “artificial” picture of the death /disease pattern in a community. It is important to examine the data carefully before standardizing. In general, the SMR or SIR is used to compare an area (e.g., health unit) with one other area (e.g., Ontario). This indirect form of standardization requires a comparator that has a large population and stable age-specific rates. SRATEs, on the other hand, are generally used to compare a number of rates at the same time, e.g., health units across a region or rates over time. This direct form of standardization requires all comparators to have relatively stable age-specific rates. For more information about standardization, refer to the Resources section: Direct Standardization (SRATES) and Indirect Standardization (SMRs, SIRs).

Cross-References to Other Sections

• Enteric Disease Hospitalization

References

• Evans AS, Brachman PS. Bacterial Infections in Humans: Epidemiology and Control. Springer, 1998.
• Evans AS, Kaslow RA. Viral Infections of Humans: Epidemiology and Control. Springer, 1997.
• Heymann DL. Control of Communicable Diseases Manual. American Public Health Association, 2004.
• P. Michel, JB Wilson, SW Martin, RC Clarke, SA McEwen, CL Gyles. A Descriptive Study of Verotoxigenic Escherichia coli (VTEC) Cases Reported in Ontario, 1990-1994. Canadian Journal of Public Health, Volume 89(4), July/August 1998;253-257.
• JD Greig, P Michel, JB Wilson, AM Lammerding, SE Majowicz, J Stratton, JJ Aramini, RK Meyers, D Middleton, SA McEwen. A Descriptive Analysis of Giardiasis Cases Reported in Ontario, 1990-1998. Canadian Journal of Public Health. Volume 92(5), September/October 2001;361-365.
• SE Majowicz, P Michel, JJ Aramini, SE McEwen, JB Wilson. Descriptive Analysis of Endemic Cryptosporidiosis Cases Reported in Ontario, 1996-1997. Canadian Journal of Public Health. Volume 92(1),January/February 2001;62-66.
• Middleton D. Descriptive Epidemiology of Enteric Disease due to Microbial Causes in Ontario: 1998. PHERO, Volume 11(5), May 26, 2000;76-85.
• Michel P, Wilson JB, Martin SW, Clarker RC, McEwen SA, Gyles CL. Temporal and Geographical Distributions of Reported Cases of Escherichia coli O157:H7 Infection in Ontario. PHERO, Volume 11(7), July and August 2000;164-171. Reprinted from Epidemiology and Infection, Vol 122, No. 2 (April 1999).
• Michel P, Wilson JB, Martin W, Clarke RC, McEwen SA, Gyles CL. Estimation of the under-reporting rates for the surveillance of Escherichia coli O157:H7 cases in Ontario, Canada. PHERO, Volume 12(2), February 25, 2001;54-61. Reprinted from Epidemiology and Infection (2000), 125, 35-45.
• Dawson K. Data Quality in RDIS: Issues related to Combining Data Sets. Central East Health Information Partnership, October 2000. 
• Rajda Z, Middleton D. Descriptive epidemiology of enteric illness for selected reportable diseases in Ontario, 2003. Canadian Communicable Disease Report 2006;32(23):275-85.
• Rajda Z, Middleton D. Descriptive epidemiology of enteric diseases in Ontario, 2002. Public Health Epidemiology Report Ontario 2004;15(4).
• Majowicz SE, Edge VL, Fazil A, McNab WB, Doré KA, Sockett PN, Flint JA, Middleton D, McEwen SA, Wilson JB. Estimating the under-reporting rate for infectious gastrointestinal illness in Ontario.Can J Public Health. 2005;96(3):178-81.
  

Changes to Indicator May 2008 

• Added Incidence of Cyclosporiasis and Listeriosis as specific indicators
• Removed "Comparable Health Indicators" section as no longer relevant and added the link to this indicator into the "Corresponding Indicator(s) from Other Sources" section 
• Updated data source from RDIS to iPHIS and removed HELPS as a data source for population estimates
• Removed bullet "Suppress numbers <5 or rates and proportions based on counts less than 5" from "Analysis Check List" section
• Removed "Analysis Check List" section on RDIS and replace it with details on iPHIS
• Updated "Indicator Comments" section to include information on iPHIS and the conversion of RDIS data into iPHIS
• Added updated references
  

Date of Last Revision: May 7, 2008.