How Dangerous Are Oysters, Really?

In light of the New Orleans Saints Superbowl appearance this Sunday, Food Safety News ran this story on a gulf coast favorite, oysters. It gives a brief history of oyster consumption and a synopsis of the risks you take when you eat these delectable bivalves. Specifically, raw oysters can be (and somewhat frequently are) contaminated with one of several strains of a bacteria called Vibrio. Vibrio can be a minor inconvenience akin to run of the mill food poisoning, but if you happen to be immunocompromised or have impaired liver function it can be a heck of a lot worse. If you fall into one of these at risk groups, eating contaminated oysters can lead to a nasty condition called "primary septicemia." The mortality rate for "primary septicemia" is over 50%.

So two big questions:

First, why are restaurants allowed to serve us contaminated oysters? To start with, whether they can depends on where you live. Some states, like California, have taken steps to ensure that all oysters sold or served are clean. If your state doesn't have a law like this on the books, it's probably no surprise. The gulf oyster industry has done a whole lot of work and spent a whole lot of money to keep their product as loosely regulated as possible. They are able to succeed in large part because vibrio occurrs naturally in marine environments, so it can't really be considered an adulterant in the sense of being something "unnatural".

Second, and even more important, what can you do to protect yourself from bad oysters? If you fall into one of the at-risk groups, your best bet is to avoid oysters altogether, or at the very least to cook them thoroughly. If you do plan on eating oysters (and I for one definitely do), you can heed the advice of consumer adovacay group Center for Science in the Public Interest and avoid oysters harvested from Gulf Coast waters from April to October. Oysters harvested in colder waters (like those in New England or the Pacific Northwest) are much less likely to be contaminated, since vibrio is naturally present only in warmer water.