• The incidence rate is the total number of new cases of infectious diseases relative to the total population (per 100,000) in a specified time period.
• Age-specific incidence rates are the annual number of new cases of infectious diseases in a given age group per 100,000 population in that age group in a specified time period.
• Age-standardized incidence rate (SRATE): the number of new cases of infectious 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 infectious diseases to the number expected if the population had the same age-specific incidence rates as Ontario.

• Incidence of Chickenpox (Varicella) 
• Incidence of Diphtheria
• Incidence of Haemophilus influenzae b disease, invasive
• Incidence of Hepatitis B (acute)
• Incidence of Influenza
• Incidence of Measles
• Incidence of Meningococcal disease, invasive
• Incidence of Mumps
• Incidence of Pertussis
• Incidence of Poliomyelitis, acute (indigenous and imported)
• Incidence of Rabies (human)
• Incidence of Rubella
• Incidence of Rubella, congenital syndrome
• Incidence of Tetanus

• Incidence of Acquired Immunodeficiency syndrome  (AIDS) 
• Incidence of Chlamydial infections 
• Incidence of Gonorrhoea
• Incidence of Hepatitis C
• Incidence of human immunodeficiency virus (HIV) infection
• Incidence of Syphilis (primary, secondary and congenital)

• Incidence of Amebiasis 
• Incidence of Botulism
• Incidence of Campylobacter enteritis 
• Incidence of Cholera 
• Incidence of Cryptosporidiosis
• Incidence of Cyclosporiasis
• Incidence of Food Poisoning, All Causes
• Incidence of Gastroenteritis, Institutional Outbreaks
• Incidence of Giardiasis
• Incidence of Hepatitis A
• Incidence of Listeriosis  
• Incidence of Paratyphoid Fever
• Incidence of Salmonellosis
• Incidence of Shigellosis
• Incidence of Trichinosis
• Incidence of Typhoid Fever
• Incidence of Verotoxin-producing Escherichia coli (VTEC) infection
• Incidence of Yersiniosis

• Incidence of confirmed new active and re-treatment tuberculosis
• Incidence of confirmed tuberculosis cases resistant to any one antibiotic
• Incidence of confirmed cases of Multi-Drug Resistant (MDR) tuberculosis
• Incidence of latent tuberculosis infections (LTBI)

• Incidence of Lyme Disease
• Incidence of malaria
• Incidence of West Nile Virus (WNV) illness

• None.

Comparable Health Indicators: Select "View" under latest issue and then "Data Tables")
http://www5.statcan.gc.ca/bsolc/olc-cel/olc-cel?catno=82-401-x&lang=eng

• Incidence rate for invasive meningococcal disease
• Incidence rate for measles 
• Incidence rate for Haemophilus influenza b (invasive) (Hib) disease
• Incidence rate for chlamydia
• Rate of newly reported HIV cases
• Incidence rate for tuberculosis
• Incidence rate for Verotoxogenic E. coli
  

• Consider aggregation of data values and/or cell suppression when dealing with small numbers to avoid risk of confidentiality breach. A new resource is currently under development to provide more detailed information on this issue.
• 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 a case): Encounter (or Episode) Type = Case AND Diagnosis Status = Confirmed. For carriers, Encounter Type = Carrier AND Diagnosis Status = Carrier. For HIV cases, Encounter Type = Carrier. For LTBI Episode Type = LTBI.
• Be aware that some diseases can occur more than once within the same person.
  

total number of new cases in the specified time period

total population in the specified time period

total number of new cases in the specified time period in an age group

total population in the specified time period in that age group

Sum of (age-specific rate of new cases in x 1991 Canadian population in that age group) 

Sum of 1991 Canadian population

Sum of new cases in the population

Sum of (Ontario age-specific rate x population in that age group)

• Age groups for age-specific rates: <1, 1-4, 5-9, 10-19, 20-44, 45-64, 65-74, 75+, Total
• Sex: male, female.
• Geographic areas: public health unit
• Immigrant status: Canadian born vs foreign born

• 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.¹ Some cases may also be double-counted among people who move or cross various health unit boundaries.There were some issues around data integrity when RDIS first began operation in 1990. In some cases, case definitions have changed over time. Refer to Case Definition Comparison Document (publichealthontario.ca username and password required).
• 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 Case Definition Comparison Document (publichealthontario.ca username and password required).
• There may be considerable under-reporting of actual cases for some diseases. 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: Standardization of Rates.

Vaccine Preventable Diseases

• The diseases listed in this indicator are all preventable through adequate immunization.
• Chickenpox data are not collected in the same manner as other vaccine preventable diseases. Chickenpox data are collected at an aggregate, rather than an individual, level. Discuss this issue with immunization staff prior to analysis.

• Syphilis has several stages: congenital, primary, secondary and latent. The rate of congenital syphilis is one indicator while the rate of combined primary and secondary syphilis is a second indicator. Latent syphilis is not used in the calculation of rates since such persons are usually not infectious and represent previous infections.

• The incidence of enteric diseases is typically highest among children under the age of 4.

• An increased proportion of tuberculosis cases are due to immigration from endemic areas and increased prevalence of HIV infections.
• Multi-drug resistance (MDR) is an increasing concern globally and needs to be monitored in Canada. Rates of resistance to any one of the antibiotics (particularly Isoniazid or Rifampin) is important for program planning.

• None

Cited References

1. Dawson K. Data Quality in RDIS: Issues related to Combining Data Sets. Central East Health Information Partnership, October 2000.

• 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.

• Sciberras J. Measles Incidence in Ontario – Impact of the 1996 Immunization Campaign. PHERO, Volume 8 (1), January 31, 1997; 4-6.
• Sciberras J. Invasive Haemophilus Influenzae Serotype B Surveillance – Documenting the Progression Towards Elimination. PHERO, Volume 10(1), January 29, 1999;1-4.
• National Advisory Committee on Immunization. Canadian Immunization Guide, Seventh Edition, 2006. Ottawa, ON: Public Health Agency of Canada, 2006. Available at http://www.phac-aspc.gc.ca/publicat/cig-gci/index-eng.php 
• Public Health Agency of Canada. CCDR 2006;32S3:1-44. Canadian National Report on Immunization, 2006. Available at: http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/06vol32/32s3/index.html
• Public Health Agency of Canada. Final Report of Outcomes from the National Consensus Conference for Vaccine-Preventable Diseases in Canada. CCDR 2007;33S3:1-56. Available at: http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/08vol34/34s2/index-eng.php

• Public Health Agency of Canada. 2004 Canadian Sexually Transmitted Infections Surveillance Report. CCDR 2007;33S1:1-69. Available at: http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/07vol33/33s1/index_e.html

• Alexander D. Epidemiology of AIDS/TB coinfection in Ontario – 1990-1995. PHERO, Volume 8(4), April 25, 1997;94-98.
• Kerbel C. Epidemiology of Tuberculosis in Ontario 1995. PHERO, Volume 8(4), April 25, 1997; 81-93.
• Tuberculosis Prevention and Control, Public Health Agency of Canada, and the Canadian Lung Association/Canadian Thoracic Society. Canadian Tuberculosis Standards, 6th Edition. Ottawa, ON: Public Health Agency of Canada, 2007. Available at: http://www.phac-aspc.gc.ca/tbpc-latb/pubs/tbstand07-eng.php

• 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. Available at: http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/06vol32/dr3223ea.html
• 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.
• Liu et al. Descriptive epidemiology of verotoxin-producing E. coli reported in Ontario, 1996-2005. CCDR. 1 April 2007, Vol 33, Num 7. Available at: http://www.phac-aspc.gc.ca/publicat/ccdr-rmtc/07vol33/dr3307ea-eng.php
• Government of Canada. National Integrated Enteric Pathogen Surveillance Program
  (C-EnterNet) 2005-2006. Guelph, ON: Public Health Agency of Canada, 2006. Available at: http://www.phac-aspc.gc.ca/publicat/2007/c-enternet05-06/areport05-06-eng.php