The doctors, writing in the medical journal BMJ Case Reports, described how a 32-year-old man in Portugal was left in agony for a week with severe tummy pain, vomiting and fever.
A new study gives sushi eaters a reason to take it easy, reporting there's been an uptick in anisakiasis, a stomach infection caused by a worm that lives in fish, but can easily relocate to your stomach or intestines.
"When humans eat raw or undercooked infected fish or squid, they ingest nematode larvae", said a statement on the Centers of Disease Control and Prevention website. Doctors at a hospital found the worm "firmly attached" to his gut lining, which had become swollen and was causing him severe pain and nausea.
After they removed the larvae with a net, the man's symptoms soon cleared up.
Anisakiasis, an illness caused by eating parasite-contaminated fish or seafood, is on the rise in Western countries where eating sushi and other raw or undercooked fish and seafood dishes has gained popularity, according to a report published Thursday in BMJ Case Reports.
A study in the British Medical Journa l says the rise in the number of parasitic infections such as anisakiasis could be linked to eating sushi.
Most cases of the parasite have previously occurred in Japan, but the disease has been increasingly recognized as a problem in the West, the authors wrote.
The researchers in that case said at the time that raw fish prepared at home can contain anisakis and other risky parasites because the fish may not have been frozen beforehand - a process typically rendered in sushi restaurants that kills the larvae.
The ministry is calling on people to choose fresh fish and remove internal organs swiftly, avoid eating internal organs uncooked and look at fish closely and remove anisakis if found. Freezing will kill these parasites.
"There is a need to better estimate and understand the burden of disease worldwide (especially in those countries where consumption of raw or undercooked fish is common)", Bao said.
"This will ensure that any undetected Anisakis larvae are killed".