[mgcross]

And the majority of sushi has been frozen, killing any parasites. If the fish has not been frozen, there is still a risk from parasites.

[JoeAltmaier]

By law in America, its frozen in liquid nitrogen?

[evgen]

By law in most places it is frozen to at least -31F for between 15 and 72 hours and sometimes up to a week. Apparently for best quality retention the fish is 'superfrozen' as soon as it is caught by packing it in dry ice 'snow' and chilling it with liquid nitrogen to get it down to -80F or so, and it can be stored up to two years at this temp.