News Release
January 14, 2021

Today, Toronto Public Health (TPH) will launch a retrospective case-control study to identify exposure settings and activities that are associated with significantly increased risk of becoming infected with COVID-19 in Toronto. This study will include a focus on residents who recently tested negative for COVID-19 – a new approach for public health units in Canada – and will focus on issues like work environments, living arrangements and other activities including social gatherings or visits to public spaces.


Findings will compare the activities of people who test positive versus those who test negative to help understand how people may have acquired their infection and inform public health actions to help reduce virus spread. To make this comparison, the survey will collect information from residents who recently tested negative for COVID-19.


People who tested negative will receive an automated text message from 1-833-929-2338 with a link to complete the survey. The survey will include confidential and voluntary questions about an individual’s activities in the days before the COVID-19 test, the same questions about daily activities that are asked of people who test positive. Questions will focus on an individual’s living arrangements, their work environments and other activities including social gatherings or visits to public spaces. Results will help identify settings and activities that are associated with increased risk of acquiring COVID-19 infections.


The survey takes approximately 10 to 15 minutes to complete and participants are asked to complete the survey no later than three days after receiving it.


All survey responses will be kept confidential and only summary level data will be reported to protect privacy. More information about the survey is available online.




“This is one more example of the work Toronto Public Health is doing to help combat COVID-19 in our community. I encourage residents who are contacted by the survey to take part and help our medical health professionals protect our city. I continue to urge all residents to remain vigilant and follow the public health guidelines. Stay home as much as possible, wear a mask when you go outside, distance yourself from others and stick with your household.”

– Mayor John Tory


“When it comes to fighting COVID-19, knowledge is power. Understanding why some people who may have been exposed to the virus but do not contract COVID-19 is as important as understanding why others do become ill. Toronto Public Health’s new case-control study – a first among public health units in Canada – will provide us with more information about virus transmission and inform decisions about how best to protect people and stop the spread of this virus.”

– Councillor Joe Cressy (Spadina-Fort York), Chair of the Board of Health


“These comparison data will help us understand how different behaviours, settings and activities can increase a person’s risks for becoming infected with COVID-19. The information will then be used to identify which activities and settings place the individuals who contracted COVID-19 at increased risk of infection, where they may have been exposed to the virus and inform actions. We will report back on our findings about this initiative and ways to help limit opportunities for virus spread to protect our community.”

– Dr. Eileen de Villa, Medical Officer of Health


Toronto is home to more than 2.9 million people whose diversity and experiences make this great city Canada’s leading economic engine and one of the world’s most diverse and livable cities. As the fourth largest city in North America, Toronto is a global leader in technology, finance, film, music, culture and innovation, and consistently places at the top of international rankings due to investments championed by its government, residents and businesses. For more information visit the City’s website or follow us on Twitter, Instagram or Facebook.

Toronto Public Health Media Relations