Local Stats: Cases & Outbreaks

Respiratory diseases are caused by organisms such as viruses or bacteria that affect the respiratory system (e.g., lungs and throat). The organisms can be spread by coughing, sneezing or face-to-face contact.

Influenza: The influenza virus or “flu” is a respiratory virus that circulates in Ontario, most frequently in the fall and winter. Influenza spreads from person-to-person through coughing, sneezing or having face-to-face contact. It can cause mild to severe respiratory disease. While anyone can get influenza, the very young, the elderly and people with certain medical conditions are at higher risk of complications.

COVID-19: COVID-19 is a respiratory illness caused by the SARS-CoV-2 virus. It first emerged in late 2019 and quickly spread worldwide, resulting in a global pandemic. The virus primarily spreads through respiratory droplets when an infected person coughs, sneezes, or talks, and it can also be transmitted by touching contaminated surfaces. COVID-19 can cause a range of symptoms, from mild respiratory issues to severe pneumonia and multi-organ failure, with older adults and those with underlying health conditions being particularly vulnerable.

Syndromic surveillance monitors the rate of disease occurrence through a voluntary network to assess changes in the health of the larger population. Data collected in a syndromic surveillance system can be used to signal trends, identify outbreaks, and monitor disease burden in a specific geographical area and/or community. Syndromic surveillance is conducted only at selected locations called sentinel surveillance sites. In the Leeds, Grenville and Lanark District we conduct syndromic surveillance of our hospital emergency department visits and hospital admissions for evidence of respiratory infection activity. We also test two municipal sewage treatment sites for the evidence of COVID-19 and influenza viral activity in our region.

Measuring molecular viral particles in wastewater can be used as an early indicator to help detect COVID-19 and influenza in a community. People with active COVID-19 or influenza infections shed the virus in their urine and stool, sometimes even before symptom onset. This viral shedding can occur for a few days to several weeks. The presence of viral particles in sewage suggests some level of COVID-19 or influenza activity in the population using that sewer system. A key advantage of active Wastewater Surveillance is that a single test represents data from everyone in the community using that wastewater system (including those with symptoms, those without symptoms, and those who have recovered from their infection). Data collected from Wastewater Surveillance allows for centralized measuring of the level of viruses which can help shed light on whether the number of infected people in the Leeds, Grenville and Lanark District Health Unit region is increasing, decreasing, or staying the same.

Leeds, Grenville and Lanark District Health Unit currently has two Wastewater Surveillance sites reporting (Brockville and Smiths Falls). As our region is more rural than urban, many of our residents use independent septic systems or wastewater treatment systems that cannot support Wastewater Surveillance testing. This is a limitation as to how much Wastewater Surveillance testing can be done. However, the detection of positive Wastewater Surveillance signals in our urban centers indicates that COVID-19 or influenza is circulating in our region.

Different settings and different viruses have separate criteria when declaring an outbreak. The criteria is based on the risk factors of the populations residing in the setting.

COVID-19:  Two or more residents or patients who are epidemiologically linked (e.g., within a specified area, unit, floor, or ward), both with positive results from a PCR, molecular, or rapid antigen test, within a seven-day period. Both cases must have reasonably acquired their infection within the setting.

For other respiratory infections: Two cases of acute respiratory infections (ARI), within 48 hours with any common epidemiological link (e.g., unit, floor), and at least one case 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).

COVID-19 case and vaccination rates have been recalculated using the recently released Census of Canada 2020 population counts from Statistics Canada. We had been using the 2020 Ministry of Finance calculation. The 2020 Census has indicated that our population has grown by about 4% in Leeds, Grenville and Lanark since 2016. These population estimates will now be used by the Health Unit in our rate calculations going forward in both our weekly vaccination dashboard and daily COVID-19 case summary dashboard. This will provide a more complete and accurate picture of our population’s COVID-19 case and vaccination rates. However, changing our population counts have resulted in some of our reported statistics changing as well. Our reported vaccination rates by age group have decreased along with our overall vaccination rates. The result is that the COVID-19 rates and vaccination rates in the daily COVID-19 Surveillance Dashboard and the weekly COVID-19 Vaccine Dashboard have decreased slightly. 

The Ministry of Health is not currently using the recently released Census of Canada 2020 population data from Statistics Canada, so the denominator they are using for Leeds, Grenville and Lanark is still from the 2020 Ministry of Finance calculation. Our epidemiologists worked quickly to incorporate this new data into our local dashboard as soon as possible to reflect the current population of the area. The integrity of our statistics is important to us. Slight fluctuations in data are normal when compiling statistics and adjustments are sometimes necessary; we have always been committed to providing the most accurate statistics possible.

Occasionally, data entry errors will result in a client being assigned to the wrong age grouping when their COVID-19 vaccine information is entered into the COVAX system. This results in some age groups where the client count is actually larger than the census count for that age group, giving a total percentage vaccinated that is larger than 100%.

Influenza is rarely lab-tested for in Ontario. Even when an influenza test is completed by a laboratory, public health is often not notified of the results. Most times public health only becomes aware of influenza-related hospitalizations are when they are linked to an outbreak in a high risk setting such as a long-term care facility or retirement home. Because of this, influenza hospitalizations are not a valid indicator of disease prevalence or severity for respiratory virus surveillance.