Respiratory virus data tracker frequently asked questions (FAQs) |
How are data on infectious disease cases collected? |
The Health Department receives notifications of positive laboratory results for all disease of public health significance for Durham residents from all Ontario laboratories. These results are received electronically or by fax and entered into the provincial database Integrated Public Health Information System (iPHIS). |
Why are case counts for COVID-19 no longer available? |
Due to changes in the provincial data system, confirmed COVID-19 cases are no longer available for reporting. Durham Region Health Department continues to monitor respiratory virus using the best available data. This includes COVID-19 test positivity data to monitor COVID-19 activity in the community. |
How are COVID-19 deaths counted? |
A COVID-19 death reported on the Data Tracker is a death resulting from a clinically compatible illness in a confirmed COVID-19 case. The number of deaths includes those for which COVID-19 is the underlying cause of death, COVID-19 contributed to but was not the underlying cause of death, and those with type of death listed as unknown or missing. It excludes deaths where the cause of death is unrelated to COVID-19 (e.g., trauma).
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When is an outbreak declared in an institution? |
An institutional outbreak is one that occurs in a long-term care home (LTCH), retirement home (RH) or hospital. Outbreaks in congregate living settings such as group homes and shelters are not counted as institutional outbreaks.
For LTCHs and RHs, a confirmed COVID-19 outbreak is currently defined as: two or more residents with a common epidemiological link (e.g., same unit, floor, etc.), each with a positive molecular or rapid antigen test, within a 7-day period, where both cases have reasonably acquired their infection in the home.
Epidemiological link is defined as reasonable evidence of transmission between residents/staff/visitors and there is a risk of transmission of COVID-19 to residents within the home.
For hospitals, a confirmed COVID-19 outbreak is defined as two or more patients with a common epidemiological link (e.g., within a specified area/unit/floor/ward), both with positive results from a polymerase chain reaction (PCR) test OR rapid molecular test OR rapid antigen test within a 7-day period where both cases have reasonably acquired their infection in the acute care facility.
COVID-19 outbreak definitions have changed throughout the pandemic. Prior to April 8, 2021, only one case of COVID-19 occurring in a resident or staff was needed for an outbreak to be declared in a LTCH or RH.
A confirmed respiratory infection outbreak (other than COVID-19) is defined as two cases of acute respiratory infections (ARI) within 48 hours with any common epidemiological link (e.g., unit, floor), at least one of which must be laboratory-confirmed, or three cases of ARI (laboratory confirmation not necessary) occurring within 48 hours with any common epidemiological link (e.g., unit, floor).
Any outbreak where influenza was identified is reported under the appropriate influenza category (Influenza A or Influenza B) regardless of what other virus is also identified in the outbreak. Examples of respiratory infections include rhinovirus, metapneumovirus and parainfluenza virus.
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 COVID-19 guidance for public health units on LTCHs, RHs and on the congregate living settings on acute care settings, and on other respiratory infection outbreaks in long-term care homes.
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What is a confirmed case? |
Confirmed case definitions for each infectious disease of public health significance are provided on the Ministry of Health website. The Data Tracker reports only confirmed cases who are residents of Durham Region. |
Why are your numbers sometimes different from what is reported provincially or by hospitals? |
Health statistics including infectious disease case counts, COVID-19 positive tests, hospitalizations, deaths, and institutional outbreaks from the provincial systems are dynamic and always changing. The day that the data are extracted can make a big difference because data are continually being processed.
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Why did the total number of hospitalizations change in June 2024? |
Due to changes in the provincial data system hospitalization data about Durham Region residents is no longer available for reporting. From June 12, 2024 onwards, the Respiratory Virus Data Tracker presents information about COVID-19 hospitalizations from bed census data from hospitals in Durham Region. This data includes residents from outside of Durham who are hospitalized in Durham hospitals, resulting in larger total hospitalization counts than previously reported. This is a change in measurement, and does not reflect changes in respiratory virus activity.
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COVID-19 wastewater surveillance frequently asked questions (FAQs) |
How does the SARS-CoV-2 virus end up in wastewater? |
People with COVID-19 can shed the SARS-CoV-2 virus in their stool, although the amount of the virus shed varies from person to person. This shedding happens regardless of whether a person has symptoms, has been tested for, or diagnosed with COVID-19. The amount of virus in wastewater can be measured by collecting samples from wastewater treatment plants. When combined with public health data, this information can provide an estimate of COVID-19 infection trends in the community.
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How are data on COVID-19 in wastewater collected? |
Durham Region Works Department collects wastewater samples hourly for 24 hours approximately five times per week from the Corbett Water Pollution Control Plant (WPCP) and three times per week from the Darlington WPCP. Each sample represents the community that is contributing wastewater to that specific WPCP site.
The samples are shipped to Ontario Tech University, where they are analyzed to extract and detect RNA fragments from the SARS-CoV-2 virus which causes COVID-19 infection. The PCR detection methods used for wastewater are very similar to those used in clinical testing from nasopharyngeal swabs. However, since COVID-19 viral fragments are present in very low concentrations in wastewater, the lab uses special scientific methods to first capture the viral particles from wastewater before extracting the viral RNA. This ensures accurate and consistent detection using a highly sensitive PCR detection method.
Wastewater samples are collected across the province as part of Ontario’s Wastewater Surveillance Initiative (WSI). Public Health Ontario reports the wastewater signal for Ontario and its sub-regions in its report on COVID-19 Wastewater Surveillance in Ontario.
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Why did the number of sampling sites in Durham Region decrease in April 2023? |
The Ontario Ministry of the Environment, Conservation and Parks (MECP) has been responsible for managing and funding Ontario’s Wastewater Surveillance Initiative (WSI) since fall 2020. The MECP, in partnership with academic laboratories, municipalities and public health units, created a comprehensive and internationally recognized wastewater surveillance network across Ontario. As a result of a comprehensive review of data from all Ontario wastewater sites and consultations with public health units, the MECP launched a new network of sampling sites as of April 1, 2023. The WSI changes were made to represent each public health unit area, provide early warning or confirmation of trends, support public health and health care decision-making, and focus resources on sites that provide results with the least amount of duplication.
For Durham Region, the number of sites reduced from seven to two, with an additional site identified for emergency sampling if needed. The frequency of testing in the Corbett Water Pollution Control Plant (WPCP) in Whitby increased from three times to five times per week in the expectation that more frequent sampling and a shorter lag time would be more effective as an early warning system. The sites of Corbett and Darlington WPCPs provide very good representation of the Durham Region population.
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How is the wastewater trend determined? Sometimes it looks like it is increasing or decreasing but is categorized as "stable". |
The trend in COVID-19 viral signal in wastewater is calculated for the past 14 days based on data from at least three samples. No Recent Data” refers to when there were fewer than three samples collected over the past 14 days. The trend is assessed using a linear regression model, which provides two key pieces of information to categorize trend, direction, and statistical significance.
- The direction of the trend tells us if the COVID-19 signal in wastewater has increased or decreased over the past 14 days.
- The statistical significance tells us how likely the 14-day trend could be due to chance.
How we categorize the 14-day wastewater trend is illustrated in the figure below.
![How we categorize the 14-day wastewater trend is illustrated in the figure below. How we categorize the 14-day wastewater trend is illustrated in the figure below.](/en/health-and-wellness/resources/Images/Wastewater-Trend-Flowchart.png)
For the 14-day trend to be categorized as increasing or decreasing, it must be statistically significant (P<0.1). If it is not significant (e.g., likely due to chance), the trend is categorized as stable.
It is possible for the trend to look like it is decreasing, as shown by the purple line in the graph below but be categorized as "stable" if the trend is not statistically significant. When there are more samples, there is more precision and an estimate is more likely to be statistically significant, particularly when there is consistency in the direction where most or all samples are going down or going up. If there are fewer samples and less consistency, the trend is less likely to be statistically significant and more likely to categorized as "stable".
![The trend looking like it is decreasing by the purple line but be categorized as "stable". The trend looking like it is decreasing by the purple line but be categorized as "stable".](/en/health-and-wellness/resources/Images/Wastewater-Sigvs-Trend-Example.png)
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Why is there such a lag between the time when samples are collected and when results are reported? |
There are many steps in the process of analyzing and reporting wastewater results. Since samples are collected hourly for 24 hours, a full day is required for sampling. Samples are then transported to Ontario Tech University for analysis. Due to the unknown composition of wastewater, which may contain compounds other than human excreta, and the sensitivity of viral RNA to water temperature and composition, researchers at Ontario Tech University must use high quality reagents and equipment to process and analyze the samples, while meeting all safety protocols. This process takes approximately 8-10 hours from when the samples first arrive at the lab and when results are obtained.
Following analysis, the results are uploaded to the Ontario Wastewater Surveillance Data Hub, managed by the Ministry of the Environment, Conservation and Parks (MECP). MECP process the data and make them available the same day or within 24 hours from when the labs upload their results. These data are then extracted by the Health Department and posted on the Data Tracker weekly. The amount of time required to collect, transport, process, and analyze the wastewater samples results in a reporting lag.
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Can you estimate the number of cases from the wastewater signal? |
It is difficult to estimate the number of COVID-19 cases in the community from wastewater because so many factors influence the wastewater signal, including how much virus individuals shed and who is moving in and out of the community during the day. There is some evidence that people infected with some sub-variants of Omicron may shed more virus leading to higher wastewater signals but not necessarily higher numbers of people with COVID-19. Increases in COVID-19 levels in wastewater over multiple samples may indicate increasing transmission within the community. However, individual samples with unusually high levels may not be indicative of increasing transmission as they are not as precise as looking at the overall trend. The signal can fluctuate greatly from sample to sample. |
What cautions are there to the interpretation of wastewater data? |
- Wastewater surveillance for COVID-19 is a new and rapidly evolving field, and we are continually learning more about how to interpret the connection between COVID-19 in wastewater and the level of COVID-19 infection in the community.
- Although people with COVID-19 can shed the SARS-CoV-2 virus in their stool, current research indicates the viral fragments found in wastewater are not infectious. Additionally, all water discharged from treatment plants is treated to remove viruses and bacteria and monitored to ensure compliance with provincial regulations.
- We recommend caution when interpreting daily and short-term variation in the viral signal results since the ability of wastewater surveillance to represent the residents of a community is impacted by the ways people travel in and out of these communities for work, school, and leisure.
- COVID-19 viral concentrations in wastewater are not comparable across sampling sites due to differences, like:
- The characteristics of the wastewater system and the types of inputs it receives (e.g., residential, industrial, commercial)
- The physical components of the wastewater system
- The distance wastewater travels to reach the treatment plant or pumping station where it is sampled for testing
- Results should only be compared to understand general patterns and trends
- Emerging research suggests that a higher level of infection is needed to be able to detect COVID-19 in wastewater samples from wastewater facilities that serve smaller communities like Darlington.
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Respiratory virus summary reports |
Check out our epidemiological reports to learn more about respiratory virus activity in Durham Region
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Status of COVID-19 in Ontario |
For information regarding the status of COVID-19 in Ontario, including Durham Region, see the Ontario Respiratory Virus Tool. |
Definitions |
Confirmed influenza cases |
The total number of Durham Region residents with laboratory confirmation of influenza infection. Individuals infected more than once will have each infection counted as a new case. For the influenza case definition, see the Ministry of Health website. |
COVID-19 hospitalizations |
The number confirmed new admissions for COVID-19 within Durham Region hospitals, this includes people who live outside of Durham Region but who are patients in Durham hospitals. |
Deceased COVID-19 cases |
Reflects the number of deaths resulting from a clinically compatible illness in a confirmed COVID-19 case. It includes deaths for which COVID-19 is the underlying cause of death, COVID-19 contributed to but was not the underlying cause of death, and those with type of death listed as unknown or missing. It excludes deaths where the cause of death is unrelated to COVID-19 (e.g., trauma). There may be a time delay between receiving the test result or notice of the death and entering the death into iPHIS. |
Reported date |
Refers to the date the case was reported to public health. |
Episode date or Onset date |
Is the best estimate of when the disease started and refers to the date when symptoms first appeared, or if not available, the date the sample was taken for the laboratory test. |
Percentage of positive tests |
The percentage of positive tests among all COVID-19 laboratory tests conducted in Durham Region residents that week. As of December 31, 2021, PCR testing in Ontario was focused on higher risk individuals who were more likely to test positive, pushing the percent positivity up.
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Data sources |
- COVID-19 Outbreaks and Deaths up to June 1, 2024: Public Health Case and Contact Management (CCM) Solution.
- COVID-19 Outbreaks and Deaths June 2, 2024 onwards, all Influenza Cases, and all Influenza and other Respiratory Outbreaks: Integrated Public Health Information System (iPHIS).
- COVID-19 Laboratory Test and Percent Positivity: Ontario Laboratories Information System (OLIS).
- COVID-19 Hospitalizations: Ontario Ministry of Health Bed Census Summary.
- Wastewater Viral Signal: Ontario Wastewater Surveillance Initiative viral SARS-CoV-2 RNA detection; in partnership with Toronto Metropolitan University and Ontario Tech University.
- Secondary and Elementary School Absences (Durham District School Board, Durham Catholic District School Board, Kawartha Pine Ridge District School Board, Peterborough Victoria Northumberland and Clarington Catholic District School Board, and Conseil scolaire Viamonde): school board absenteeism reporting to the Health Department.
- Child Care Absences: voluntary child care centre absenteeism reporting to the Health Department, response rates vary by week.
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Data tracker feedback |
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