Sushi lovers, beware: scientists have just found out something about this food that should cause you great alarm if you eat it on a regular basis. Although it’s been praised as an awesome food both because it is low in fat and high in protein, not to mention rich in Omega 3 fatty acids, a new report finds that there is a dangerous parasite lurking inside sometimes that is causing more problems than ever before.

The report, published in the medical journal BMJ Case Reports, discusses the case of a Portugal man who began experiencing stomach pain and then started vomiting and reported a high fever. Doctors determined that he had recently eaten sushi, and after an endoscopy, they found a parasite larvae that had attached itself to his stomach lining.

They diagnosed him with anisakiasis, which is caused by parasitic worms that can be found in sushi, and as the food rises in popularity, so do cases of this unpleasant disease.

“An unseen hazard of eating raw or undercooked fish/seafood is on the rise in Western countries, where dishes, such as sushi, are becoming increasingly popular, warn doctors today,” the statement from BMJ reads. “The warning comes after they treated a 32 year old previously well man who had had severe upper gut (epigastric) pain, vomiting, and fever for a week. A blood test indicated mild inflammation, and the area below his ribs was tender. But it was only when the man revealed that he had recently eaten sushi that the doctors suspected that he might have anisakiasis.”