Ever read an online review alleging food poisoning at a restaurant you’re considering trying and wondered whether you should trust it? A new report suggests that such reviews may sometimes flag real incidents that might otherwise go unreported.

According to the new study, published in the Journal of the American Medical Informatics Association, consumer review site Yelp helped the New York City Department of Health and Mental Hygiene spot 10 outbreaks of foodborne illness from New York City restaurants between 2012 and 2017.

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City officials used a special program developed by Columbia University scientists, which scanned Yelp reviews for keywords (including “sick,” “vomit,” and “food poisoning”), in order to flag potential food poisoning incidents.

“Identifying foodborne illness outbreaks can be challenging because not all individuals with foodborne illness are tested, and therefore they’re not reported to health departments,” says Thomas Effland, a Ph.D. student in the computer science department at Columbia University and lead author of the study. “Additionally, individuals may not report suspected outbreaks to public health agencies.”

While the Columbia University program has been used to spot foodborne illness only in New York City, the study authors hope to expand the program to other areas. Similar ideas are also catching on across the country. Harvard Medical School, the Chicago Department of Public Health, and the Southern Nevada Health District, for example, all monitor tweets related to foodborne illness to help find and track potential outbreaks.

Here, what you should consider when using social media to report or spot a potential food poisoning outbreak, and what to do if you get sick:

How the Program Worked

New York City epidemiologists used the Columbia University program as a starting point: Once the program flagged food poisoning keywords in Yelp reviews, the investigators then tried to interview some of the reviewers to find out more details about the illness—such as symptoms, whether other dining companions got sick, and what else the reviewer had eaten recently.

While Columbia’s report reveals that their program may be helpful for uncovering food poisoning incidents that haven’t been reported through more traditional channels, Consumer Reports’ experts say that online reviews may not always be a trustworthy source of information.

According to James E. Rogers, Ph.D., director of Food Safety Research and Testing at Consumer Reports, online user reviews may contain errors or may mistakenly attribute an unrelated bout of illness to a restaurant.

“I would be wary of depending solely on user reviews from Yelp or other sites to steer me away from a restaurant,” Rogers says.

Instead, he says to consult your local public health site, such as the NYC Department of Health, to check media releases for active outbreaks. “Occasionally, if outbreaks are national,” Rogers says, “the Food and Drug Administration or the Centers for Disease Control and Prevention will provide information.”

Rogers says other aggregation websites and blogs, such as Iwaspoisoned.com and the Food Poison Journal can be helpful to cross-reference a restaurant review that mentions a potential problem.

Luther Lowe, vice president of public policy at Yelp, says that ensuring the accuracy of the information on the site is a top priority. Yelp rolled out a pilot project in San Francisco in 2015 that alerts its users to restaurants that received low food safety scores from the city’s health department. This warning system, however, is not yet available in the rest of the U.S.

What to Do If You Get Sick

Foodborne illnesses can be caused by many different bacteria, viruses, or parasites, and the symptoms and the speed of their onset can vary widely. According to the FDA, you might feel sick within hours of eating a contaminated food, or it might take weeks or even a month to experience symptoms—one reason it’s difficult for consumers to figure out exactly which meal made them sick.

Nevertheless, if you think you might have gotten food poisoning after eating at a particular restaurant, the CDC says to report it to your local health department. (The CDC offers resources for finding the best contact for your county or city.)

Health officials may ask what you’ve eaten and where, and may also ask you to provide a stool sample, Rogers says. If you still have any of the tainted food in your fridge or freezer, it’s smart to hold onto it for possible testing. (Any potentially tainted food you’re holding onto should be wrapped securely and clearly labeled “do not eat,” Rogers says.)

Most cases of food poisoning clear up in a few days. According to the American Academy of Family Physicians, the most important thing is to stay hydrated by drinking water (if you can keep it down). When you start to feel better, ease back into eating with bland foods such as crackers, toast, and bananas.

If your symptoms are severe—such as bloody diarrhea, dehydration, vomiting, or a fever of 101.5° F or higher—or if you have diarrhea that lasts longer than three days, seek medical attention. Your doctor should report any suspected case of foodborne illness to the appropriate public health agency.