issues and experts

SFU epidemiologists urge caution as COVID-19 infections see renewed spike

July 21, 2020


Caroline Colijn, Canada 150 Research Chair in Mathematics for Evolution, Infection and Public Health,

Paul Tupper, professor, Department of Mathematics, 604.314.8671,

Shradhha Sharma, University Communications and Marketing, 604.202.2504,

Link to preprint paper:


While British Columbia saw a steady drop in the number of coronavirus infections over the last few months, the recent spurt in new cases has SFU professors Caroline Colijn and Paul Tupper urging people to be cautious.

The latest preprint paper co-authored by the researchers provides details of a new framework designed to help guide which interventions–including physical distancing, masks and other barriers to transmission, or social bubbles–are likely to have the most impact, and in which settings. 

The researchers hope such information will be useful in considering re-opening economies with principled measures to reduce COVID-19 transmission. They have created a framework to help resolve some of the uncertainty around the effectiveness of different interventions.

Using data from reported events where transmissions occurred and were well characterized, they introduce the concept of ‘event R’, the expected number of new infections due to the presence of a single infected individual at an event.

The researchers determine a fundamental relationship between ‘event R’ and four parameters—transmission intensity, duration of exposure, the proximity of individuals and the degree of mixing—then weigh which interventions, from physical distancing to hand washing, are likely to have the most impact, and in which circumstances.

While B.C. has seen cases drop over the past months, the recent spike has renewed concerns to better understand what works.

“Many organizations are tasked with making arrangements to re-open while attempting to reduce COVID-19 risk in the near-complete absence of information about which measures will be most effective in their particular setting,” says Colijn, who holds a Canada Research Chair in Mathematics for Evolution, Infection and Public Health.

The findings could help formulate policy for provinces gradually entering Phase 3 of reopening across Canada, as well as the potential pitfalls public health officials could avoid globally as countries try to reopen economies and lift restrictions on movement.

The research is currently in preprint and not yet peer-reviewed.

Colijn and Tupper are available for interviews this week.


About Simon Fraser University: 

As Canada’s engaged university, SFU works with communities, organizations and partners to create, share and embrace knowledge that improves life and generates real change. We deliver a world-class education with lifelong value that shapes change-makers, visionaries and problem-solvers. We connect research and innovation to entrepreneurship and industry to deliver sustainable, relevant solutions to today’s problems. With campuses in British Columbia’s three largest cities – Vancouver, Burnaby and Surrey – SFU has eight faculties that deliver 193 undergraduate degree programs and 127 graduate degree programs to more than 35,000 students. The university now boasts more than 160,000 alumni residing in 143 countries.