Restaurant review websites like Yelp can help health inspectors track down unreported outbreaks of food poisoning, a pilot project in New York City has found.
Reviews posted on Yelp helped inspectors identify previously unknown food-poisoning outbreaks at three restaurants involving 16 people, said senior investigator Dr. Sharon Balter, medical epidemiologist for the New York City Department of Health and Mental Hygiene.
Officials said that they ended up citing each of the restaurants with multiple health violations that might otherwise have gone undetected.
"We know we don't identify all of the outbreaks that are out there, and this is just another tool to do that," Balter said.
Details of the pilot project are described in the May 23 issue of the U.S. Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.
In the project, inspectors combed through Yelp using a software program designed at Columbia University to seek out reviews that mentioned foodborne illness. Yelp set up a private data feed that provided its publicly available reviews in an easy-to-search format.
"We have a lot of reviewers and a lot of restaurants in New York, which made this a good place to try it out," Balter said.
About half of all local food-poisoning outbreaks occur at restaurants, according to the CDC.
The New York program evaluated about 294,000 restaurant reviews over a nine-month period. Balter said it looked for evidence of potential food-poisoning outbreaks in the reviews, including:
- Keywords indicating illness.
- Cases of two or more people reported ill at one restaurant.
- Reports that indicated enough time had passed that an illness could have been caused by a foodborne bacteria, and not some other cause.
The software ended up identifying 468 potential cases of recent food poisoning, of which only 15 had been reported to the nonemergency 311 line dedicated to reporting such cases, Balter said.
Upon further investigation, health inspectors verified three small outbreaks from those cases and launched investigations.
The three outbreaks involved a December 2012 meal in which a house salad caused seven out of nine people in a party to get sick; a January 2013 meal of shrimp and lobster cannelloni that sickened three of five people in a party; and a March 2013 meal of macaroni and cheese spring rolls that caused all six people in a party to get sick.
The outbreaks occurred due to problems like cross-contamination, bare-hand contact with ready-to-eat food, improper food storage and improperly sanitized work surfaces, the inspectors found.
The inspectors suspect these outbreaks likely sickened even more people than were identified. "We assume when we do outbreak investigations that there were other people who got sick we didn't know about," Balter said.
Balter did not find it discouraging that hundreds of complaints of illness on Yelp resulted in only a handful of confirmed outbreaks. She noted that of the 3,000 or so food-poisoning complaints received by the 311 service each year, only about 1 percent end up confirmed as a restaurant-related outbreak.
"In any surveillance system like this, there will be a lot of noise," she said. "The exciting thing for us is we could sort through that noise and find actual cases."
The New York City inspectors said they plan to continue using the software to scan for possible food-poisoning outbreaks. They will refine their methods by performing daily, instead of weekly, scans of Yelp reviews, and will expand the project to include other review sites.
For more on foodborne illness outbreaks, visit the U.S. Centers for Disease Control and Prevention.