In July, there was a recall on two brands of plant-based milks, Silk and Great Value, after a listeria outbreak that led to at least 20 illnesses and three deaths. Public health officials determined the same strain of listeria had been making people sick for almost a year. When Globe reporters began looking into what happened, they found a surprising fact: the facility that the bacteria was traced to had not been inspected for listeria in years.

The reporters learned that in 2019 the Canadian Food Inspection Agency introduced a new system that relies on an algorithm to prioritize sites for inspectors to visit. Investigative reporters Grant Robertson and Kathryn Blaze Baum talk about why this new system of tracking was created, and what went wrong.