Research
My research is in population biology, mathematical modelling, evolutionary epidemiology, species range shifts, infectious diseases and public health.
I am interested in the biological questions. I like to learn new mathematical frameworks, so there are fewer technical barriers to answering the biological questions I am interested in. I have made models that are delay differential equations, partial differential equations, integrodifference equations, non-autonomous ordinary differential equations, branching process models, and models that use optimal control. I aim to not to be limited in the questions that I can answer, by the models that I know. I like to develop new methods, rather than use existing methods without understanding and extending them.
It is important to understand the general dynamics of models. When I see time-series data, I ask “what types of models, and interacting biological processes, could give rise to these data?” I like to study the full range of model dynamics to be able to answer that question.
Our modelling during COVID-19
Our modelling work during the COVID-19 pandemic began with a technical report that was included in witness testimony when travel measures implemented under the public health emergency were challenged in provincial court. Our technical report showed that travel measures reduced clinical COVID-19 cases in Newfoundland and Labrador by 92%. This work is now peer-reviewed, published, and cited in a World Health Organization report for the Western Pacific Region.
The travel measures remained in place after the court decision, and subsequently during the COVID-19 pandemic, Newfoundland and Labrador implemented a containment strategy. Most SARS-CoV-2 infections were reported in travelers and were contained without spread to members of the Newfoundland and Labrador community. This lack of community spread meant that classic models such as Susceptible-Infected-Recovered, and widely-adopted methodologies for calculating dynamic reproduction numbers in partially-immune populations, were not appropriate. We needed to develop novel methodologies to assess the effectiveness of public health measures, and the capacity to relax measures given increasing vaccination levels in the Newfoundland and Labrador community. This work is peer-reviewed and published in this theme issue on Modelling COVID-19 and Preparedness for Future Pandemics.
The technical annex to a World Health Organization update (July 2021) establishes regional factors as considerations to determine whether travel measures are appropriate (see bullet points at the bottom of p2). Our accepted publication describes regional considerations that determine whether an elimination strategy is appropriate, where implementing an elimination strategy potentially requires implementing travel restrictions. Particularly, we emphasize that the recommended strategy, elimination or mitigation, may not be the same for all Canadian jurisdictions. This work is to appear in the Royal Society Open Science, Science, Society, and Policy collection. International Advisory Board members for this collection include Professor Mona Nemer, Chief Science Adviser to the Prime Minister of Canada.
Some of our COVID-19 work is ongoing. We have completed an analysis of the travel declaration forms submitted by non-residents during the public health emergency. We analyzed the results of Rapid Antigen Tests to understand under-reporting, and inform some of our ongoing modelling. We are analyzing contact tracing data, and we continue to work to advance mathematical modelling methodologies to support the needs of Canadian small jurisdictions.
I have been quoted in the British Medical Journal, the New York Times, the Globe and Mail, and local media such as NTV, the Canadian Broadcasting Corporation, and The Telegram. I appeared in a Fields Institute Panel. I was lead organizer for the AARMS-EIDM Summer School in Modelling Infectious Diseases.
Research after COVID-19
Generally, I just love mathematical modelling. Models are the power that answer questions. I like to develop models to fit to data, to estimate key parameters, and to resolve unknown, implicit, critical assumptions. I like to develop theory that demonstrates the power of mechanistic mathematical models in data analysis.
I am a population biologist. Population biology is a field that has contributed substantially to our knowledge of how infectious disease is spread. The connections between the fields of population biology and infectious disease are well-noted.
Our past work has considered adding in physiology, and temperature dependence, to describe seasonal population dynamics and species ranges shifts in response to climate warming. We have integrated dispersal, movement, and genetic diversity into population dynamic models to describe spatial dynamics and trait evolution. Our work has applications to salmon parasites, tiny clams, rabies, drug resistance in hospitals, SARS-CoV-2, bumblebees, wolves, moths, and butterflies.
Future work will consider disease establishment in new populations similar to a biological invasions framework. This work will be in the context of rabies, avian influenza, and vectorborne disease.
Publications
For my publications, see Google Scholar.
When financially possible, our publications are open access. If you can’t access a publication, please email me. Below are links to publications that may be more difficult to access. You might also search MedRxiv and BioRxiv for author-typeset copies of the publications.