A 32-year-old man from Portugal was reported to have symptoms of severe stomach pain, vomiting, and a weeklong fever after eating sushi. Through the doctors’ examination, a worm-like parasite called Anisakis was discovered sticking in an area in his stomach.

According to Web MD the doctors from Portugal believed that the man might have anisakidosis after he stated that the last thing he ate was sushi. Anisakidosis is described to be a parasitic infection. Anisakis is also described to have a length of 5 to 20 millimeters and is accumulated from eating undercooked or raw fish/seafood.

The doctors then inserted an endoscope in order to find out if the man’s case was really Anisakidosis. Afterward, the doctors then retrieved a worm-like parasite and removed its larvae with a net. With that said, the parasitic worm case was published in the journal BMJ Case Reports. Study author Joana Carmo, MD then noted that a recent study revealed that Anisakis was found in 39.4% of the fresh mackerel from different fish markets in Granada, Spain.

Live Science then reported that cod, haddock, fluke, pacific salmon, herring, flounder and monkfish, as well as squid were among the common sources of the parasitic worm Anisakis aside from sushi. Centers for Disease Control and Prevention also warned that the best way to not encounter the risk of contracting the parasite, raw or undercooked fish must be avoided.

Nonetheless, it was advised by the Food and Drug Administration that in order to kill the Anisakis parasites seafood like sushi should be cooked at an internal temperature of 145 degrees Fahrenheit (63 degrees Celsius). On the other hand, freezing fish should be done at -4 F or below for 7 days or at -31 F or below until solid, and storing at -31 F (-35 C) or below for 15 hours. While the last was instructed to be at -31 F (-35 C) or below until solid and storing at -4 F (-20 C) or below for 24 hours.