Restaurant Inspectors Are Reading Your Yelp Reviews

Three years ago, New York City’s health department was trying to track a suspected outbreak of food-borne illness that went on for weeks at a particular restaurant. One investigator, who was a fan of Yelp, looked up the restaurant’s reviews on the ratings website and saw that diners reported they’d gotten sick after eating there. The agency created a Yelp account and sent messages to the reviewers to get more information about what they and their companions had eaten, to determine which foods were responsible for the illness.

Soon after, investigators started a program to discover whether Yelp reviews could alert the Department of Health and Mental Hygiene to food-borne outbreaks it hadn’t learned about through complaints the agency gets by phone and online. (New York’s mayor at the time, Michael Bloomberg, is the majority owner of Bloomberg Businessweek parent Bloomberg LP.) The agency asked Yelp for a data feed of public reviews on New York restaurants and worked with researchers at Columbia University to develop algorithms that would flag suspect reviews—keywords such as “vomit,” “diarrhea,” and “food poisoning,” were part of the equation.