Picture of Anne WinterAnne Winter is an epidemiologist specialist at Public Health Ontario


There are a variety of mechanisms through which surveillance information about the circulation of influenza and other respiratory viruses are collected each year by public health authorities in Canada, however reporting is often skewed towards the collection of data from institutional settings such as long-term care facility respiratory infection outbreaks or reports of severe illness such as hospitalizations among laboratory-confirmed cases of influenza. There is a dearth of surveillance information from community based settings reporting less severe disease. Knowledge of circulating respiratory viruses in local communities may afford an opportunity to determine the onset of community influenza epidemics and predict the timing of institutional outbreaks.

In most Canadian provinces there is a network of community based sentinel health care providers, primarily physicians, who report weekly on a voluntary basis the number of patients who present to their practice by age group and within those age groups, the number of patients who present with ILI. This is expressed as a rate (i.e. the number of patients presenting with ILI out of all patients presenting to the practice) at either the local public health unit or provincial level. This network is managed nationally through the national FluWatch surveillance system.  In addition, there is a separate network of sentinel community practitioners who participate in the Sentinel Practitioner Surveillance Network (SPSN), which operates in British Columbia, Alberta, Ontario and Quebec. Sentinels participating in this network collect respiratory samples from eligible patients presenting to their practice with symptoms of nationally-defined ILI, and receive a nominal fee for each sample and associated laboratory requisition submitted. Information from both of these sentinel systems can act as an early warning of the start of seasonal influenza epidemics and contributes to situational awareness of the circulation and impact of a variety of respiratory viruses. Participating physicians in either program are eligible to receive MAINPRO+ credits.

Clinicians and public health authorities benefit from reports from community sentinel practitioners in order to better understand the spectrum of illness from respiratory viruses, their impact on community providers and the potential broader health sector impact, such as on emergency room visits or hospital admissions. However, because of the low number or lack of reporting sentinels, public health unit and provincial rates are highly variable in terms of week to week variation and this is why in Ontario, local ILI and provincial rates are no longer disseminated. In fact many local health units in Ontario do not have participating sentinels for either system or may have a single sentinel who reports sporadically or rarely submits respiratory samples during the year.

Traditionally a joint call out is made every year by the College of Family Physicians of Canada on behalf of Public Health Ontario to community practitioners to join either or both the national sentinel network as part of FluWatch or the SPSN; however the response rate is very low. In Ontario, less than 0.1% of physicians contacted by the College volunteer to participate as a sentinel in either system.

Screening for breast, colon, cervix and prostate cancer is standard practice for community health care practitioners and has been for many years. Such screening is conducted despite the fact that controversy exists for some screening programs, as for example with breast and prostate cancer. Conversely, screening (more commonly referred to as surveillance) for influenza-like illness (ILI) is not standard practice for community practitioners despite the fact that respiratory viruses including influenza are associated with significant morbidity and mortality. It has been estimated that in Canada an average of 3,500 deaths and 12,200 hospitalizations can be attributed to influenza infection alone each year.

While it is indisputable that community practitioners run busy practices, information generated from ILI reporting combined with laboratory surveillance data generated through the SPSN can help with clinical decision making. For example, in communities where FluWatch sentinels have reported high ILI rates and results from SPSN sentinel submissions have noted high levels of circulating influenza, clinicians would have the information needed to decide whether or not to treat high-risk patients who present for medical care with ILI with an influenza antiviral.

As well, having robust sentinel community networks can contribute to a mutual understanding of influenza and other respiratory viruses, such as the recent increase in enterovirus D68 (EV-D68) detections and monitor their geographic spread and changes in intensity as respiratory virus season progresses, benefitting both clinicians, public health and patients themselves.