Oysters are a food type that is associated with norovirus outbreaks, along with leafy greens and berries. This is in part because people tend to eat oysters raw or partially cooked, and oysters can actually concentrate enteric viruses like noroviruses in their guts if they filter feed in waters contaminated with these viruses. Still, the overall number of shellfish-associated norovirus outbreaks in this country tends to be low, and we present this one because it is an uncommon occurrence.
A few days ago, Washington state health officials closed a shellfish harvesting area in the Hammersley Inlet, as well as issued a recall of shellfish harvested from the site. 4,000 dozen oysters and 3,000 pounds of Manila clams were included in this recall, which were harvested from November 10th to December 5th. The product went to several states, including Oregon, Nevada, Florida, Minnesota, Illinois, California, New York, Maine, Georgia, Massachusetts, New Jersey, and Virginia. You can read the official recall notice here.
The closure and recall occurred because at least a dozen people became sick with norovirus-like symptoms last month (two of which were lab confirmed cases of norovirus), and it was found to be related to the consumption of oysters. The recall was possible because the state uses a tracking system for its shellfish, enabling health investigators to know when and where the implicated oysters and clams came from. One of several shellfish samples from the harvesting site sent for testing did come back positive for norovirus.
The health officials did not find a source of the contamination among the companies that harvested and shipped the shellfish, but did find a leaking septic system in the vicinity that could have been the source of the virus, which has a temporary fix while a permanent one is in the works.