If you're just sitting down with your lunch, you may want to look away now – especially if it is sushi.

Raw fish is known to come with a side-dish of danger every time you tuck in as there's always the possibility you may inadvertently consume a parasite.

By nature of their uncooked preparation, teeny tiny occupants that call many fish bodies home can survive long after the fish has died.

Often the larvae of parasitic worms, or even a worm itself, are invisible to the naked eye – making sushi eaters vulnerable to being invaded by unwanted visitors.

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If you're one of the unlucky sushi eaters this happens to, symptoms of contracting a parasitic worm can begin days, weeks or sometimes even months later.

Which is what happened to a 25-year-old woman from Tokyo who dined on a dinner of sashimi recently.

The anonymous parasite victim was admitted to the city's St Luke's International Hospital complaining of a sore throat – only for doctors to discover "a black moving worm" in her left tonsil.

If you've made it this far without throwing up, kudos to you.

The rare case, which occurred on July 8, has been documented in the American Journal of Tropical Medicine and Hygiene, where it was determined to be a Pseudoterranova azarasi, a type of parasitic roundworm.

It noted the woman had consumed a meal of "assorted sashimi" five days prior, and had suffered a sore throat ever since.

The 38mm worm removed from an unidentified 25-year-old woman after eating sashimi. Photo / American Journal of Tropical Medicine and Hygiene
The 38mm worm removed from an unidentified 25-year-old woman after eating sashimi. Photo / American Journal of Tropical Medicine and Hygiene

"The worm body was black, 38mm long, 1mm wide, and was moulting the outer cuticle," the entry reads.

"DNA and the fact that the worm was in exuviation revealed this worm was a fourth-stage larva of Pseudoterranova azarasi."

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The super gross entry also included a rather disgusting photo of the worm, which was removed using tweezers.

"Although oropharyngeal infection is rare, it is known to cause 'tingling throat syndrome' and cough5 (a sudden, forceful hacking sound)."

It is one of the varying parasites that can be consumed with raw fish, including sushi and sashimi which have become more popular in recent years, and the number of reported cases has markedly increased worldwide.