an underdone hamburger, or a hamburger that was cooked but improperly handled could contain bacteria too.

The contaminated spinach a few years ago proves how easy it is for food to get contaminated (spinach farm was downstream from a cattle farm...what goes in a cow must come out, and travel downstream into the spinach)

There's a chance that all food could harbor bacteria.

If someone's worried about sushi causing them problems with their MS from either bacteria or mercury poisoning, dont eat sushi...or at the very least, ask your doctor about it if you're that worried.