Siv was a Full Professor in the Department of Applied Mathematics at the University of Waterloo, where he was Head of the Biomedical Research Group. He was the founding Director of the Centre for Mathematical Medicine at the Fields Institute and was an active member of the Society for Mathematical Biology (SMB). He hosted the 2008 SMB Annual Meeting in Toronto and, in 2023, was elected as an SMB Fellow.

Throughout Siv’s long, fruitful career ran a consistent thread of wanting to use his talent in mathematical research to help others. Among his research interests, the most prominent included biomechanics, the mathematical modelling of clinical conditions and diseases, and mathematical oncology.  As his colleague, Professor Jane Heffernan recalls, he was a passionate applied mathematician, working to bridge mathematics and the biomedical sciences every day, through his research, teaching, collaborations, mentoring and leadership. You can hear Siv discuss his work in the SMB podcast “Biology in Numbers” here.

His work steering the Fields Centre for Mathematical Medicine, which he co-founded with Dr. Amit Oza of the Princess Margaret Hospital, held firm for almost two decades. Starting in 2008, the CMM ran numerous workshops and conferences that brought together mathematical modellers, oncologists, epidemiologists and neuroscientists, among many other disciplines, to explore the indelible partnership between mathematics and healthcare.

Siv's passing is a particular shock, as Fields had just wrapped up the Thematic Program in Mathematical Oncology this past December, where he was a regular and active participant. Professor Thomas Hillen, one of the program’s organizers and a Fields Distinguished Visitor, recalls that “many of us had the opportunity to engage with him in scientific and personal conversations. His insights and positive attitude were infectious.

“Siv gave several scientific talks during the program and one of the workshops, entitled ‘Frontiers in Computational and Mathematical Medicine,’ was dedicated to Siv’s many contributions in the field. This conference was organized by Siv’s former graduate students and postdocs. Little did we know that this celebratory conference would also be a farewell conference, and we are glad that we did have a chance to come together in person and honor his work,” he says.

As former Fields Director, Professor Kumar Murty, recalls, Siv’s most prominent features were his smiling face and enthusiastic speech. “Even if he was just telling us about the weather, he would do so with a positive energy that everyone could feel. We are grateful for his dedicated service to the Institute in many roles, but especially as head of the Centre for Mathematical Medicine since its inception. We are even more grateful for having had his company and friendship,” he says.

One of Siv’s longtime friends and collaborators, Professor Huaxiong Huang, shared memories of what a gift it was to have someone like Siv in your life. Both met as young mathematicians at a Fields event, and much of their work together centred at the Institute, both at the CMM and the Centre for Quantitative Analysis and Modelling (CQAM), which ran a parallel lab at Waterloo. They “had lunch every week” when Prof. Huang was Deputy Director at Fields, where they discussed everything from work to family and life in general.

Over the past months, they had started working on a new plan to reorganize CMM by expending its mandate to include the biotech sector as well as hospitals and international partners, in order to take advantage of the new technological advances in the areas of AI and machine learning. As Prof. Huang recalls, Siv was enthusiastic about the plan even after his recent surgery.

“His passing came as a shock, completely unexpected, and I am deeply saddened by it. I lost a good friend, Fields lost a devoted supporter, and the word lost a gentle soul.”