Case Status in Durham Region

The Health Department does not report probable cases because they represent a small number, may change status to become confirmed cases, and the definition of a probable case has changed greatly over the course of the pandemic. Refer to the Ontario Ministry of Health’s current definition.

In situations where there is an indeterminant test result or where a client initially declined to be tested, the person may subsequently undergo testing and if positive, would then be added to the Data Tracker as a confirmed case. The Ontario Ministry of Health also does not report probable cases.

The number of active cases is the number in home isolation and in hospital. The number of newly reported cases does not add up to the number of active cases because some cases are already resolved or almost resolved by the time they are reported to the Health Department. There is a time interval between when a person first develops symptoms or has close contact with a case, seeks testing and gets tested, and when the lab analyzes the test and notifies the Health Department of the positive result. If this interval is 10 days since the person first had symptoms and they are no longer sick, the case would be fully resolved. The first graph on the “time trends” tab of the Data Tracker shows that many of the cases recently reported are already resolved (active cases in green and resolved in blue). This is the nature of a dynamic information system where people are moving through different stages of a complex disease.

COVID-19 counts are produced by provincial information systems that are dynamic and always changing. The time of day that the data are extracted can sometimes make a big difference because cases are continually being processed. For example, the Health Department extracts information at 1 p.m. and updates the Data Tracker around 3 p.m., reflecting complete data as of the end of the previous day. In comparison, the Ontario Ministry of Health COVID-19 Dashboard is updated daily with data as of 1 p.m. the previous day. Public health nurses work into the evening to identify new cases and determine if any active cases have a change in hospitalization or resolved status. The provincial reports do not include cases processed in the evening and is not as up to date as the Data Tracker.

The reporting metric may also be different. For example, here are the "new cases" data reported by different sources:

• Durham Region Data Tracker: Number of cases by reported date (the date when the Health Department was first notified of the case).
• Ontario Ministry of Health COVID-19 Dashboard: Change in number of cases from the previous day (presented by data reporting date).
• Public Health Ontario Daily Epidemiological Summary: Change in number of cases from the previous day (presented by data extraction date).
• Public Health Ontario COVID-19 Data Tool: Number of cases by episode date (the best estimate of the date when the disease started) and by reported date.

The bottom line is that different sources report different numbers. The Ontario Ministry of Health states that if there is a discrepancy between numbers reported on their website and those reported publicly by a public health unit, consider the number reported by the public health unit to be the most up to date.

The Health Department extracts data at 1 p.m. to reflect COVID-19 case information as of the day before. Our public health nurses contact cases into the evening and we want to include the complete count from the whole day. In the morning, nurses finalize details in the provincial reporting system and epidemiologists conduct data quality checks on the extensive information that is uploaded to the Data Tracker, including exposure source, municipality, outbreak information, and address used for mapping to Health Neighbourhood. We need the morning to do this work. After extracting data at 1 p.m., the files are approved and uploaded around 2 p.m. The dashboard program needs an hour to complete the refresh of visuals and the Data Tracker is finally up-to-date around 3 p.m. Sometimes complexities in specific case information or large numbers of new cases can delay the update.

The Health Department receives notification of positive COVID-19 laboratory results for Durham Region residents from all Ontario laboratories. These results are received electronically or by fax. Public health nurses contact all Durham Region residents who are positive to gather detailed information about where the resident has been in the last 14 days, who the resident has been in contact with, and demographic information such as age, gender, address, race, income category, household size and language. Public health nurses document this information in the Health Department’s secure electronic health record system and enter specific data into the provincial reporting system. This provincial system for COVID-19 reporting consisted of the integrated Public Health Information System (iPHIS) from February to July 30, 2020 and the Public Health Case and Contact Management Solution (CCM) since July 31, 2020 onward.

The Health Department identifies COVID-19 patients in hospital through the following means: the public health nurse speaks directly with the client during the outreach call or to their next of kin, the hospital reports the status to public health, or the public health nurse calls the hospital directly as part of follow-up.

There are two reasons why a hospitalization may not be recorded on the Data Tracker:

1. They are not a Durham Region resident,
2. They no longer require follow-up by public health after a defined period based on Ministry of Health guidance. This corresponds to 10 days for cases with mild to moderate illness who are not severely immune comprised and 20 days for cases with severe illness requiring ICU level care or who are severely immune compromised. A case may be closed in the provincial CCM database and counted as resolved even if the person remains hospitalized for many more weeks. This person is no longer infectious and does not require public health follow-up. Note that some patients may be hospitalized for other reasons, but because they test positive for COVID-19, they are counted as a hospitalized case.

Hospitals report their own hospitalization numbers to the Ministry of Health, which may be different from those reported by public health. For provincial information about COVID-19 hospitalization, see covid-19.ontario.ca/data/hospitalizations.

Outbreaks that occur in these settings are reported on the Data Tracker under the "School & Child Care Centre Outbreaks" tab. The number of outbreak-related cases is reported by specific school and child care centre. For a COVID-19 outbreak to be declared in either setting, there must be at least two lab-confirmed cases with evidence that at least one case acquired their infection through the school or child care centre. Individual cases, such as a student who became infected in their household, does not count as an outbreak unless there is transmission to someone else in the facility. Two or more cases in a school does not automatically mean there is an outbreak. Sometimes a case has not been in the school during their infectious period. Sometimes there is no epidemiologic link between the cases or two cases may be siblings in different classes who acquired COVID-19 from their household. Whenever there is a case of COVID-19 in a school, close contacts are recommended to be tested but unless one of more of these contacts turn out to be positive and there is transmission to someone else in the school, it does not meet the definition of an outbreak.

Individual school or child care cases that are not related to an outbreak are not reported on the outbreak tab but are captured overall in the Data Tracker. The number of cases reported on a school board or provincial website may differ from those reported on the Data Tracker because schools may report both individual and outbreak-related cases as well as probable cases. Probable cases are not reported anywhere on the Data Tracker (refer to FAQ above).

The definition of an outbreak in a child care centre was changed by the Ministry of Health in November 2020 from requiring only one lab-confirmed COVID-19 case to two cases. This means that the definitions are now aligned for schools, before and after care centres, and child care centres. Respiratory infections are common in child care centres and while a general respiratory outbreak may occur, it will not count as a COVID-19 outbreak unless children or staff are tested and the virus is detected.

If a school or child care centre is not listed on the outbreak tab of the Data Tracker, there is no COVID-19 outbreak reported in that facility.

The Health Department began posting the number of workplace and community event outbreaks by category and month on the Data Tracker on January 21, 2021. We do not post the names of businesses unless there is a public health risk to the general public and we need to publicize details to ensure we are notifying potential cases and contacts that cannot otherwise be reached.

A workplace outbreak is defined as two or more positive cases of COVID-19 with evidence that transmission occurred in the workplace within a 14-day period where both cases could have reasonably acquired their infection in the workplace. As with all cases of COVID-19, the Health Department does extensive case and contact management to ensure that all potential exposures are thoroughly investigated, resulting in notification, self-isolation and testing, if necessary.

COVID-19 deaths are added to the Data Tracker if the individual died while still infected with COVID-19. This could mean they died with COVID-19 or because of COVID-19. The actual cause of death would be determined by a physician and indicated on a death certificate. Mortality (death certificate) data is not available from the province of Ontario until much later.

Public health nurses confirm the address of the case at the time that they were diagnosed with COVID-19. Small discrepancies arise in the Data Tracker when an address or postal code will not map into a neighbourhood, e.g. the address is in a new subdivision that is not yet covered by the mapping program or there is an incomplete address that will not map properly. We map by address first but if the address does not map because it is incomplete or missing, we use postal code which is less precise. In general, our address information is complete and we do data quality checks to make it as accurate as possible.

COVID-19 data is dynamic and constantly changing as the status of cases shifts from day to day. The number of cases can go down if a person positive for COVID-19 is subsequently found through additional testing to not be infected and to have initially received a false positive result. Sometimes an address is corrected and assigned to another municipality. Sometimes data quality checks find duplicate cases in the system and removing the duplicate brings the case count down. Duplicates and differences in reporting can happen between neighbouring public health units. Public health units work together to ensure accurate reporting of cases who may live in one area but work or be exposed to COVID-19 in another area. Dropping a case may not be apparent at the Durham Region level if the total number of new cases is increasing, but it may be noticeable at the municipality level where numbers are smaller.

The Health Department is conscious of presenting COVID-19 data to the community while protecting privacy and security of sensitive health information. Providing the name of a town or village where a case resides can compromise a person’s privacy and does not aid public health efforts. Assume that COVID-19 is circulating in your community – continue to practice physical distancing, wear a non-medical mask or face covering and wash your hands thoroughly and often.

An institutional outbreak is one that occurs in a long-term care home (LTCH), retirement home (RH) or hospital. An outbreak is declared when two or more lab-confirmed cases of COVID-19 are detected in a resident, patient or staff (including essential caregiver) of the home or hospital, with an epidemiological link, within a 14-day period, where at least one case could have reasonably acquired their infection in the home or hospital.

Prior to April 8, 2021, the definition of an outbreak in a LTCH or RH required that only one laboratory-confirmed case be detected in the home. As a result, there are some COVID-19 outbreaks during this time that had a total of one case.

Outbreaks in congregate living settings such as group homes and shelters are not counted as institutional outbreaks.

An outbreak is declared over based on the last case identified. When the last case is a resident of an institution, the outbreak is over when no new cases have been identified in the past 14 days since the last case became ill or was isolated. If the last case is a staff member, the outbreak is over when no new cases have been identified in the past 14 days since the last shift the staff worked.

Note that the definitions above are for surveillance purposes only. Public health units have the discretion to declare an outbreak when investigating suspected cases and conditions in institutions, including when the above definitions are not completely met, based on Ministry of Health guidance.

On the Data Tracker, outbreaks are listed in a table on the "Institutional Outbreaks" tab by alphabetical order of institutional name. You can also sort by "reported date" or "date declared over" by clicking on that heading in the table.

The Institutional Outbreaks tab presents the number of cases related to outbreaks in long-term care homes, retirement homes and hospitals located in Durham Region. There is the option to differentiate staff and residents. The Exposure Source tab provides the most likely means by which cases acquired COVID-19. Here the "Outbreak – Staff" and "Outbreak - Resident" categories include congregate living settings such as group homes and shelters, as well as institutions. While residents would include only residents of facilities located in Durham Region, "Outbreak - Staff" can include people who work in facilities located outside of Durham Region. This information is noted on the Data Tracker. As an example, a personal support worker who acquired COVID-19 while working in a long-term care home in Scarborough would not be captured in the Institutional Outbreak tab but would be counted in the Exposure Source tab under the "Outbreak - Staff" category.