How Dangerous Are Parasites? Depends Who You Ask
Despite the FDA’s blanket recommendations for the elimination of parasites, which is the main goal of its freezing guidelines, very few infections from eating raw fish have been documented in American medical literature. In the US, eating raw fish that hasn’t been frozen is rare enough that the agency’s “Bad Bug Book” uses Japan as a reference point, since the practice is far more prevalent there. But even in Japan, where freezing of fish meant for sashimi is not required, reported infection rates are vanishingly small compared to the total population. (For instance, the Bad Bug Book reports “more than 1,000 cases” of infection by anisakis worms, the most common parasite in marine fish, reported annually in Japan, but keep in mind that’s out of a total population of ~127 million in 2015.)
Because some infections are asymptomatic, and many are thought to go unreported, the risk of infection may be greater than statistics suggest. On a less scientific level, worms—particularly parasitic worms—inhabit dark recesses of our collective imagination. The idea that eating a piece of seemingly pristine, delicious fish carries a risk of infestation by alien-like organisms is enough to give anyone—including health authorities equipped with all the relevant, fear-assuaging data—the heebie jeebies.
