Ontario Public Health Units Research Articles

Epidemiology of sporadic and outbreak-associated hepatitis A infections in Ontario, Canada: A descriptive summary, 2015-2022.

Hepatitis A is a disease of public health significance that typically causes acute, self-limiting infection. Understanding the risk factors and demographics associated with individual infections and outbreaks can guide public health communication and interventions. To assess the number of hepatitis A cases and outbreaks in Ontario from January 1, 2015, to November 22, 2022, and to identify common risk factors associated with sporadic and outbreak-associated infections in Ontario. Confirmed and probable hepatitis A cases reported between January 1, 2015, and November 22, 2022, were extracted from the Ontario electronic reporting system. Descriptive analyses were used to summarize and compare risk factors reported by sporadic and outbreak-associated hepatitis A cases. Annual rates of infection for individual public health units were calculated using annual population estimates for Ontario health regions. During the study period, 938 cases of hepatitis A were reported in Ontario (an average annual rate of 0.9 cases per 100,000 population), with 31.3% (n=294) of cases linked to one of 18 unique outbreaks of hepatitis A. Four of 13 local outbreaks were associated with elementary school settings. Reported risk factors differed between sporadic cases (predominantly travel-related) and cases linked to known outbreaks (anal-oral contact, illicit drug use, diapering/assisting in toileting, close contact with a case). Rates of sporadic infection differed across public health units in Ontario over the study period. Public health interventions that aim to increase awareness of hepatitis A risk factors and increase vaccine uptake among those at increased risk of exposure could help to reduce the incidence of both locally acquired and travel-related sporadic infections and outbreaks.

SARS-CoV-2 viral titer measurements in Ontario, Canada wastewaters throughout the COVID-19 pandemic

During the COVID-19 pandemic, the Province of Ontario, Canada, launched a wastewater surveillance program to monitor SARS-CoV-2, inspired by the early work and successful forecasts of COVID-19 waves in the city of Ottawa, Ontario. This manuscript presents a dataset from January 1, 2021, to March 31, 2023, with RT-qPCR results for SARS-CoV-2 genes and PMMoV from 107 sites across all 34 public health units in Ontario, covering 72% of the province’s and 26.2% of Canada’s population. Sampling occurred 2–7 times weekly, including geographical coordinates, serviced populations, physico-chemical water characteristics, and flowrates. In doing so, this manuscript ensures data availability and metadata preservation to support future research and epidemic preparedness through detailed analyses and modeling. The dataset has been crucial for public health in tracking disease locally, especially with the rise of the Omicron variant and the decline in clinical testing, highlighting wastewater-based surveillance’s role in estimating disease incidence in Ontario.

Supporting Ontario public health units to address adverse childhood experiences in pandemic recovery planning: A priority-setting exercise

BackgroundAdverse childhood experiences (ACEs) are potentially traumatic exposures experienced during childhood, for example, neglect. There is growing evidence that the coronavirus disease 2019 (COVID-19) pandemic and related socioeconomic conditions contributed to an increased risk of ACEs. As public health programs/services are re-evaluated and restored following the state of emergency, it is important to plan using an ACEs-informed lens. The aim of this study was to identify and prioritize initiatives or activities that Public Health Ontario (PHO) could undertake to support Ontario public health units’ work towards ACEs-informed pandemic recovery plans.MethodsThe Child Health and Nutrition Research Initiative method was adapted to conduct a priority-setting exercise (May–October 2022). Two online surveys were administered with members of the Healthy Growth and Development (HGD) Evidence Network, comprised of public health unit staff working in child and family health/HGD from Ontario’s 34 public health units. In the first survey, participants were asked to propose activities or initiatives that PHO could undertake to support Ontario public health units’ work towards ACEs-informed planning. In the second survey, participants were asked to score the final list of options against pre-determined prioritization criteria (for example, relevance). Responses were numerically coded and used to calculate prioritization scores, which were used to rank the options.ResultsIn all, 76% of public health units (n = 26) responded to the first survey to identify options. The 168 proposed ideas were consolidated into a final list of 13 options, which fall under PHO’s scientific and technical support mandate areas (data and surveillance, evidence synthesis, collaboration and networking, knowledge exchange and research). A total of 79% of public health units (n = 27) responded to the follow-up survey to prioritize options. Prioritization scores ranged from 76.4% to 88.6%. The top-ranked option was the establishment of a new provincial ACEs community of practice.ConclusionsOver three quarters of public health units contributed to identifying and ranking 13 options for PHO to support public health units in considering and addressing ACEs through pandemic recovery planning. In consultation with the ACEs and Resilience Community of Practice, recently formed on the basis of this exercise, PHO will continue to use the ranked list of options to inform work-planning activities/priorities.

Variability in public health programming and priorities to address health inequities across public health units in Ontario, Canada.

In 2018, Ontario Public Health Standards were updated to include the foundational Health Equity Standard to guide planning, implementation, and evaluation of public health programs and services. Public health units (PHUs), the regional public health bodies, are now required to address health equity through four requirements: (a) Assessing and Reporting; (b) Modifying and Orienting Public Health Interventions; (c) Engaging in Multi-sectoral Collaboration; and (d) Health Equity Analysis, Policy Development, and Advancing Healthy Public Policies. This qualitative descriptive study explored how the 27 participating PHUs (out of 34) serving urban (N = 10), mixed urban-rural (N = 15), and rural (N = 9) populations addressed the Health Equity Standard. Using document analysis, we inductively and deductively coded the content of 68 PHU Annual Service Plan and Budget Submissions from a 3-year period (2018-2020) received from the 27 PHUs. Emergent categories were organized into the four requirements and one additional emergent theme: Organizational Implementation of Health Equity. The approaches of embedding health equity into PHUs' activities varied across groups. Urban PHUs presented more diverse strategies, including working with a larger number of organizations, and participating in academic research projects. We found more process standardization and greater discussion of capacity building in urban and mixed urban-rural PHUs. Rural PHUs strategically addressed the needs of their diverse populations through relationship building with Indigenous communities. Findings suggest broad implementation of health equity approaches in public health independent of PHUs' geographic size and population dispersion, though strategies and key challenges differ across units.

A Multiphase Mixed Methods Study on the Integration of a Population Health Approach in Sexual Health Programs and Services in Ontario Public Health Units.

This study investigated the extent of and factors influencing implementation of a population health approach within sexual health programming in public health. This sequential multi-phase mixed methods study combined findings from a quantitative survey assessing the extent that a population health approach was implemented in sexual health programs in Ontario public health units and qualitative interviews with sexual health managers and/or supervisors. Interviews explored factors influencing implementation and were analyzed using directed content analysis. Staff from fifteen of 34 public health units completed surveys and ten interviews were completed with sexual health managers/supervisors. From the 8 Population Health Key Elements Template, 6 elements were moderately implemented and 2 had low implementation. Qualitative findings focused on enablers and barriers to implementing a population health approach in sexual health programs and services and explained most of the quantitative results. However, some of the quantitative findings were not explained by qualitative data (e.g., low implementation of using the principles of social justice). Qualitative findings revealed factors influencing the implementation of a population health approach. A lack of resources available to health units, differing priorities between health units and community stakeholders, and access to evidence around population-level interventions influenced implementation.

Modelling COVID-19 transmission using IDSIM, an epidemiological-modelling desktop app with multi-level immunization capabilities

The COVID-19 pandemic has placed unprecedented demands on local public health units in Ontario, Canada, one of which was the need for in-house epidemiological-modelling capabilities. To address this need, Ontario Tech University and the Durham Region Health Department developed a native Windows desktop app that performs epidemiological modelling of infectious diseases. The app is an implementation of a multi-stratified compartmental epidemiological model that can accommodate multiple virus variants and levels of vaccination, as well as public health measures such as physical distancing, contact tracing followed by quarantine, and testing followed by isolation. This article presents the epidemiological model and epidemiological-simulation results obtained using the developed app. The simulations investigate the effects of different factors on COVID-19 transmission in Durham Region, including vaccination coverage, vaccine effectiveness, waning of vaccine-induced immunity, advent of the Omicron variant and effect of COVID-19 booster vaccines in reducing the number of infections and severe cases. Results indicate that, for the Delta variant, natural immunity, in addition to vaccination-induced immunity, is necessary to achieve herd immunity and that waning of vaccine-induced immunity lengthens the time necessary to reach herd immunity. In the absence of additional public health measures, a wave driven by the Omicron variant is predicted to pose significant public health challenges with infections predicted to peak in approximately two to three months, depending on the rate of administration of booster doses.

Environmental scan of social media usage among Ontario public health units

Social media is a relatively novel way to send and express information to a large number of people at one time. Public health units (PHUs) have started to use this forum, but there has been almost no research done on how it is being used and if the way information is presented is effective. Engagement is one way to track if something posted on a social media website is being disseminated effectively to the intended audience. If a post has a low level of engagement this means that less people saw it and read the information regardless of how many times it was posted or how much work was put into the post. This article summarizes an environmental scan completed to assess engagement from all Ontario’s PHUs’ usage of social media from January 1, 2020, to June 30, 2020. The social media platforms assessed in this scan are Facebook, Instagram, Twitter, YouTube, Tiktok, Pinterest, and Reddit. All social media platforms except Reddit are being used by PHUs in Ontario. Twenty-nine PHUs have their own social media profiles, and five have their profiles included in their municipality’s. Engagement varies by region and platform, but in general increased posting (especially on Twitter and Facebook) had a small negative effect on engagement. Posting less often but with more original or creative content leads to better engagement. Increased follower counts also accounted for higher engagement across all platforms. PHUs would best use their resources to increase follower count and post less often and include more personalized posts to effectively spread their information.

Validity, reliability, and acceptability of the Evidence-Informed Decision-Making (EIDM) competence measure.

Valid, reliable, and acceptable tools for assessing self-reported competence in evidence-informed decision-making (EIDM) are required to provide insight into the current status of EIDM knowledge, skills, attitudes/beliefs, and behaviours for registered nurses working in public health. The purpose of this study was to assess the validity, reliability, and acceptability of the EIDM Competence Measure. A psychometric study design was employed guided by the Standards for Educational and Psychological Testing and general measurement development principles. All registered nurses working across 16 public health units in Ontario, Canada were invited to complete the newly developed EIDM Competence Measure via an online survey. The EIDM Competence Measure is a self-reported tool consisting of four EIDM subscales: 1) knowledge; 2) skills; 3) attitudes/beliefs; and 4) behaviours. Acceptability was measured by completion time and percentage of missing data of the original 40-item tool. The internal structure of the tool was first assessed through item-subscale total and item-item correlations within subscales for potential item reduction of the original 40-item tool. Following item reduction which resulted in a revised 27-item EIDM Competence Measure, a principal component analysis using an oblique rotation was performed to confirm the four subscale structure. Validity based on relationships to other variables was assessed by exploring associations between EIDM competence attributes and individual factors (e.g., years of nursing experience, education) and organizational factors (e.g., resource allocation). Internal reliability within each subscale was analyzed using Cronbach’s alphas. Across 16 participating public health units, 201 nurses (mean years as a registered nurse = 18.1, predominantly female n = 197; 98%) completed the EIDM Competence Measure. Overall missing data were minimal as 93% of participants completed the entire original 40-item tool (i.e., no missing data), with 7% of participants having one or more items with missing data. Only one participant (0.5%) had >10% of missing data (i.e., more than 4 out of 40 items with data missing). Mean completion time was 7 minutes and 20 seconds for the 40-item tool. Extraction of a four-factor model based on the 27-item version of the scale showed substantial factor loadings (>0.4) that aligned with the four EIDM subscales of knowledge, skills, attitudes/beliefs, and behaviours. Significant relationships between EIDM competence subscale scores and education, EIDM training, EIDM project involvement, and supportive organizational culture were observed. Cronbach’s alphas exceeded minimum standards for all subscales: knowledge (α = 0.96); skills (α = 0.93); attitudes/beliefs (α = 0.80); and behaviours (α = 0.94).

Preliminary instrument development to measure implementing a population health approach in sexual health.

This study aims to describe the preliminary development and validation of an instrument to measure the extent that a population health approach was applied in sexual health by public health units in Ontario, Canada. Preliminary scale development and administration occurred in two phases that included item development and validity testing. Two phases of development included: (1) using literature and expert input (n=6) to develop items; and (2) validation of items by content experts (n=5) and pre-testing (n=3). The validated scale consisted of 69 items across the eight key elements of a population health approach. 15 out of 35 health units completed the survey, representing 43% of health units. Instrument administration revealed that Focus on the Health of Populations and Address the Determinants of Health and their Interactions were implemented more frequently compared to Collaborate Across Sectors and Levels and Employ Mechanisms for Public Involvement, which were infrequently implemented. This preliminary scale is a way for sexual health programs to measure the extent that a population health approach is implemented by their organization. Further testing with a broader sample is needed to strengthen generalizability and address reliability.

Developing an Indigenous cultural safety micro-credential: initial findings from a training designed for public health professionals in southern Ontario

ABSTRACT Cultural safety training is a resource that healthcare institutions and staff can rely on to end anti-Indigenous racism in their organisations and to shift service providers’ attitudes, beliefs, and knowledge of Indigenous people. The aim of this study was to understand the initial knowledge and interest about Indigenous Peoples that a southern Ontario public health unit’s (PHU) staff hold. A cultural safety micro-credential project was developed in consultation with the PHU. An online survey was administered from January to March 2021 to those who were starting the micro-credential during this timeframe (n = 31). Thirty-one staff responded. A majority of the participants indicated that they had some knowledge of Indigenous Peoples and that this knowledge was relevant to their work. The number of interactions with Indigenous Peoples varied by role. Common themes for the open-ended responses included culture, relationships, and supports/services. Many of the open-ended responses highlighted feelings of not knowing enough and wanting to learn more about Indigenous Peoples. These results indicate a shift in attitudes, behaviours, and knowledge of Indigenous Peoples among the PHU staff. Cultural safety training can serve to address knowledge gaps and contribute to creating the systemic change needed to end anti-Indigenous racism in healthcare institutions.

Exploring the context, role and impact of public health nursing during COVID-19: A multiple case study protocol.

AimThe purpose of this study is to: (a) describe public health nursing roles over the course of the COVID‐19 pandemic in Ontario, Canada; (b) describe the contextual factors that influence public health nursing role implementation; and (c) describe nurses' perceived impact of their roles on client outcomes and professional/personal nursing practice.DesignDescriptive multiple case study.MethodsRecruitment of public health nurses (PHNs), working in direct service or administrative leadership positions, in an Ontario public health unit will be conducted through purposive and snowball sampling. Nursing roles will be compared and contrasted across three cases differentiated by geographic setting: urban, urban–rural, northern. In each geographic case, a priori estimates of sample size will include 10 PHNs providing direct care and at least five nurses in an administrative leadership role; with an overall estimated study sample size of 45 individuals. Demographic data will be collected using an online anonymous survey. Individual semi‐structured interviews with PHNs, and focus groups with nursing administrators will be conducted via telephone and audio‐recorded. Individual interviews and focus groups will be transcribed verbatim. Reflexive thematic analysis will be used to generate emergent themes in each case and cross‐case synthesis will be used to compare and contrast patterns across geographic cases.DiscussionExpected findings will provide an in‐depth analysis of the rapidly evolving roles and functions of PHNs throughout the COVID‐19 pandemic and their impact on individuals, families and communities. As well, findings will provide a new understanding about the contextual barriers and facilitators of PHN role implementation in their working environments.ImpactStudy findings can support decision‐making in relation to funding, resource allocation and supportive work structures and processes at a public health system and/or individual public health organization level.

Influences on the uptake of a population health approach to sexual health programs in Ontario public health units: a qualitative descriptive study.

AimPopulation-level prevention initiatives are the cornerstone of public health practice. However, despite this normative practice, sexual health programming within public health has not utilized this approach to the same extent as other public health programs. Understanding requirements to put a population-level approach into practice is needed. The objective of this study was to explore the barriers and facilitators experienced by sexual health programs and services within public health when implementing a population health approach.Subject design and methodsThe principles of qualitative description guided all sampling, data collection and analysis decisions. Data collection involved in-depth semi-structured interviews with 12 sexual health managers and/or supervisors from ten Ontario public health units. Directed content analysis was used to code and synthesize the data. Data collection and analysis was guided using constructs from the Consolidated Framework for Implementation Research.ResultsFactors that served as either barriers and facilitators to implementing a population health approach, were mainly in the inner and outer setting domains of the Consolidated Framework for Implementation Research. Participants identified the presence of community partnerships, adequate staff training on population health, and access to data on population health served as facilitators. In comparison, barriers to implementation included a lack of resources (human, financial) and clinicians’ value of and preferences for delivering services at the individual clinic level.ConclusionSome clear barriers and facilitators influenced if staff in sexual health programs and services could implement a population health approach. Results indicate where public health resources need to be enhanced to move toward a population health approach and provide insight into what worked and should be considered by public health organizations.

Beach water monitoring practices and challenges in Ontario Public Health units

Public Health Units (PHUs) in Ontario regularly monitor public beaches for E. coli levels as an indicator of the risk of recreational water-induced illness. Provincial guidance for beach water monitoring allows local flexibility in the beach monitoring process. We conducted a survey of public health professionals responsible for beach water management in Ontario PHUs to determine how monitoring practices differ across jurisdictions. We obtained data from 22 of the 29 PHUs that conduct beach water monitoring. Six health units reported meeting guidelines (27%) and four reported meeting historical water quality (18%) were important factors in deciding sampling frequency. Major challenges and limitations in monitoring that arose from the lag time between sampling and obtaining results were reported by 12 (55%). Predictive modelling has been trialled eight times across the province with varied results. This study provides an overview on the current state and future avenues for beach water monitoring in Ontario.

Public Attitudes During the Second Lockdown: Sentiment and Topic Analyses Using Tweets From Ontario, Canada.

Objective: This study aimed to explore topics and sentiments using tweets from Ontario, Canada, during the second wave of the COVID-19 pandemic. Methods: Tweets were collected from December 5, 2020, to March 6, 2021, excluding non-individual accounts. Dates of vaccine-related events and policy changes were collected from public health units in Ontario. The daily number of COVID-19 cases was retrieved from the Ontario provincial government’s public health database. Latent Dirichlet Allocation was used for unsupervised topic modelling. VADER was used to calculate daily and average sentiment compound scores for topics identified. Results: Vaccine, pandemic, business, lockdown, mask, and Ontario were six topics identified from the unsupervised topic modelling. The average sentiment compound score for each topic appeared to be slightly positive, yet the daily sentiment compound scores varied greatly between positive and negative emotions for each topic. Conclusion: Our study results have shown a slightly positive sentiment on average during the second wave of the COVID-19 pandemic in Ontario, along with six topics. Our research has also demonstrated a social listening approach to identify what the public sentiments and opinions are in a timely manner.

A pragmatic evaluation of a public health knowledge broker mentoring education program: a convergent mixed methods study

BackgroundPublic health professionals are expected to use the best available research and contextual evidence to inform decision-making. The National Collaborating Centre for Methods and Tools developed, implemented, and evaluated a Knowledge Broker mentoring program aimed at facilitating organization-wide evidence-informed decision-making in ten public health units in Ontario, Canada. The purpose of this study was to pragmatically assess the impact of the program.MethodsA convergent mixed methods design was used to interpret quantitative results in the context of the qualitative findings. A goal-setting exercise was conducted with senior leadership in each organization prior to implementing the program. Achievement of goals was quantified through deductive coding of post-program interviews with participants and management. Interviews analyzed inductively to qualitatively explain progress toward identified goals and identify key factors related to implementation of EIDM within the organization.ResultsOrganizations met their goals for evidence use to varying degrees. The key themes identified that support an organizational shift to EIDM include definitive plans for participants to share knowledge during and after program completion, embedding evidence into decision-making processes, and supportive leadership with organizational investment of time and resources. The location, setting, or size of health units was not associated with attainment of EIDM goals; small, rural health units were not at a disadvantage compared to larger, urban health units.ConclusionsThe Knowledge Broker mentoring program allowed participants to share their learning and support change at their health units. When paired with organizational supports such as supportive leadership and resource investment, this program holds promise as an innovative knowledge translation strategy for organization wide EIDM among public health organizations.

A commentary on a flawed public health investigation.

The possibility of hepatitis C being transmitted between dental patients was the genesis of an extensive and expensive look-back investigation conducted by an Ontario Public Health Unit. This investigation was performed with a minimal knowledge of nosocomial infections of dental origin, an enthusiastic reliance on untested checklist indicators and an absence of any of the criteria justifying such an investigation. As a consequence, the entire exercise was based on the false premise that an infection control lapse had occurred. This commentary will address these flaws, and other aspects of the Public Health Unit's response that detracted from its credibility. The provision of a realistic assessment of disease transmission in dentistry should result in Public Health Units conducting informed and mutually beneficial inspections of dental practices.

Relative risks of COVID-19 fatality between the first and second waves of the pandemic in Ontario, Canada

ObjectivesTo examine whether the case fatality rate (CFR) of COVID-19 decreased over time and whether the COVID-19 testing rate is a driving factor for the changes if the CFR decreased. MethodsAnalyzing COVID-19 cases, deaths and tests in Ontario, Canada, we compared the CFR between the first wave and the second wave across 26 public health units in Ontario. We also explored whether a high testing rate was associated with a large CFR decrease. ResultsThe first wave CFR ranged from 0.004 to 0.146, whereas the second wave CFR ranged from 0.003 to 0.034. The pooled RR estimate of second wave COVID-19 case fatality, compared with first wave, was 0.24 (95% CI: 0.19-0.32). Additionally, COVID-19 testing percentages were not associated with the estimated relative risk (P=0.246). ConclusionsThe COVID-19 CFR decreased significantly in Ontario during the second wave, and COVID-19 testing was not a driving factor for this decrease.

Distributing Publicly-Funded Influenza Vaccine-Community Pharmacies' Perspectives on Acquiring Vaccines from Public Health and from Private Distributors in Ontario, Canada.

Objectives: To explore community pharmacies’ experience with two models of distribution for publicly-funded influenza vaccines in Ontario, Canada—one being publicly-managed (2015–2016 influenza season) and one involving private pharmaceutical distributors (2016–2017 season). Methods: Online surveys were distributed to community pharmacies across Ontario during the 2015–2016 and 2016–2017 influenza seasons with sampling proportional to Ontario Public Health Unit catchment populations. Quantitative data were analyzed descriptively and inferentially and qualitative data were summarized for additional context. Results: Order fulfillment appeared more responsive with the addition of private distributors in 2016–2017, as more pharmacies reported shorter order fulfillment times (p < 0.01); however, pharmacies reported significantly more days with zero on-hand inventory in 2016–2017 (p < 0.01), as well as more instances of patients being turned away due to vaccine unavailability (p < 0.05). In both seasons, a similar proportion of pharmacies reported slower order fulfillment and limited order quantities early in the season. Improved availability early in the season when patient demand is highest, more vaccines in a pre-filled syringe format, and better communication from distributors on product availability dates were recommended in qualitative responses. Conclusions: Introducing private distributors for the management and fulfillment of pharmacies’ orders for the publicly funded influenza vaccine appeared to have mixed results. While key concerns surrounding the frequency, responsiveness, and method of delivery were addressed by this change, challenges remain—in particular, acquiring sufficient vaccine early in the season to meet patient demand. As pharmacies become more prominent as vaccination sites, there are several opportunities to ensure that patient demand is met in this setting.

UV, ozone, and COVID-19 transmission in Ontario, Canada using generalised linear models

BackgroundQuantifying the impact of environmental factors on COVID-19 transmission is crucial in preventing more cases. Ultraviolet (UV) radiation and ozone (O3) have reported antimicrobial properties but few studies have examined associations with community infectivity of COVID-19. Research suggests UV light can be preventative while the effect of O3 is contested. We sought to determine the relationship between UV, O3, and COVID-19 incidence in Ontario, Canada. MethodsIn our time series analyses, we calculated daily incidence rates and reproductive number (Rt) from 34,975 cases between January and June 2020 across 34 Ontario Public Health Units. We used generalised linear models, adjusting for potential confounders, to calculate point estimates (PE) and 95% confidence intervals (CI) for UV and O3. Analyses were further stratified by age groups and outbreaks at institutions versus community. ResultsWe found that 1-week averaged UV was significantly associated with a 13% decrease (95% CI: 0.80–0.96) in overall COVID-19 Rt, per unit increase. A negative association with UV was also significant among community outbreaks (PE: 0.88, 95% CI: 0.81–0.96) but not institutional outbreaks (PE: 0.94, 95% CI: 0.85–1.03). A positive association of O3 with COVID-19 incidence is strongly suggested among institutional outbreak cases (PE: 1.06, 95% CI: 1.00–1.13). ConclusionOur study found evidence to support the hypothesis that higher UV reduced transmission of COVID-19 and some evidence that ground-level O3 positively influenced COVID-19 transmission. Setting of infection should be strongly considered as a factor in future research. UV and O3 may explain some of COVID-19's seasonal behaviour.

Using Google Data to Estimate the Effects of Regional Mobility on Daily COVID-19 Cases: Evidence from Ontario Public Health Units

From September 2020 onwards, COVID-19 cases have rapidly increased across Canada. This study estimates the effects of Google population mobility indicators on daily COVID-19 cases to evaluate the impacts of public movements across different regions in Ontario. We focus on Ontario as Google mobility data are available for Public Health Units (PHUs) for that province. Results based on pooled data from May 1st – November 15th imply that higher mobility at retail stores is significantly correlated with an increase in daily COVID-19 cases. However, empirical estimates from individual PHU level time-series models reveal regional differences, as these findings are based primarily on the relationship between retail mobility and daily cases for the Public Health Units (PHUs) of Toronto and Peel. These results support the implementation of region-specific lockdowns. Further, different specifications generate daily COVID-19 forecasts for Peel and Toronto that are on average, approximately 6%-9% different from actual values. The models of this research should be of value to local health authorities who are in search of simple models that are not computationally intensive and are capable of generating reliable forecasts for specific regions.