Yelp is the newest resource for government inspectors trying to track down cases of food poisoning. By sorting through restaurant reviews left on Yelp, New York City's Health Department has been able to identify and investigate disease outbreaks, ultimately finding food-handling violations at restaurants that otherwise would have gone unnoticed.

The method was resource intensive, but it workedAn initial trial was conducted in partnership with Yelp and Columbia University for nine months between 2012 and 2013. Yelp provided an easily parseable stream of public reviews left on restaurants throughout the city, and a computer analyzed all of those for signs that they included complaints of illness. From around 294,000 reviews, 893 were automatically flagged, and manual review found that 56 percent of them were actually about potential food poisoning. The department attempted to contact 129 reviewers, whose comments sounded consistent with a disease outbreak, but only heard back from 27 of them. From those, they ended up finding three restaurants with multiple violations.

That's a small final number, and New York City's Health Department admits that using this method can be relatively resource intensive. But they say that it's something that other health departments should consider: diners appeared not to know about New York's existing health reporting line, and they expect that people will increasingly be posting their complaints through various forms of social media. "By incorporating website review data into public health surveillance programs, health departments might find additional illnesses and improve detection of foodborne disease outbreaks in the community," reads a report describing their results that's being published today by the Centers for Disease Control and Prevention.

New York City plans to continue the project, expanding it to tap into even more restaurant review websites to improve its results. It also says that it could potentially find more issues by expanding the criteria it uses to narrow down the flagged reviews, which were meant to be fairly specific during the trial. One of the other big troubles with searching through Yelp is that the Health Department wants to interview the people complaining before they investigate further, and that means they have to message those reviewers over Yelp and hope for a response.

This type of method for identifying health issues isn't entirely new — Google's data has long been analyzed to discover flu trends, and similar analysis has been done on tweets. But the investigators say that reviews can be useful in a much different way than Google's data, allowing them to identify outbreaks on a small scale and at their source. So far, it's proven to be an effective way to find ongoing issues, and New York City's Health Department thinks they could become even more useful if there was just an easy way for them to get in touch with reviewers complaining of illness.