If you’re a sushi lover, there’s some bad news for you. Despite its glowing reputation as both a delicious and ultra healthy food that is both low in fat and high in protein, a new report claims that something very alarming may be within: it carries a dangerous parasite in many circumstances.

BMJ Case Reports, a medical journal, published the report this week, pointing to the case of a 32-year-old man from Portugal who suffered from some stomach pain for more than a week, and then started vomiting and had a high fever. After doctors questioned him, they realized he had recently eaten sushi.

After an endoscopy, they found a parasite larvae that had attached itself to the lining of his stomach. Anisakiasis is the name of the parasitic worms, and scientists are seeing it on the rise thanks to the popularity of sushi.

“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 BMJ statement 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. Anisakiasis is caused by eating raw or undercooked fish/seafood infected with nematode parasites of the species Anisakis.”