They "may have been exposed to human fecal waste" and norovirus.
Your patients may want to be picky about their oysters, clams, mussels, and whole and roe-on scallops for a while. FDA says the stuff Korea has been shipping over may be contaminated.
"A comprehensive FDA evaluation determined that the Korean Shellfish Sanitation Program (KSSP) no longer meets the sanitation controls specified under the United States’ National Shellfish Sanitation Program," the agency reports. "The FDA’s evaluation found significant deficiencies with the KSSP including inadequate sanitary controls, ineffective management of land-based pollution sources and detection of norovirus in shellfish growing areas."
FDA pulled Korean shippers off the Interstate Certified Shellfish Shippers List on May 1, so you're unlikely to see fresh molluscs from Korea. But frozen or canned ones might still get through.
"Although the heat treatment that canned products undergo should eliminate the risk of norovirus," says FDA, "the contents of the cans of molluscan shellfish from Korea are still considered not fit for human food because the products were harvested from waters subject to human fecal contamination."
No Americans have been reported sickened by the Korean seafood since December.