Washington's Mason County Oysters Cause Norovirus-like Illnesses for a Second Time in 3 Months



Oysters Harvested from Hood Canal

Cause Norovirus-like Illnesses

 

One more "wee beastie" to worry about.

A second outbreak from norovirus carried by Mason County oysters?
Oysters harvested from in Washington's Mason County have again caused what the Department of Health describes as "norovirus-like illnesses." DOH has not yet said whether the oysters have tested positive for norovirus, nor whether the source is the harvest site in Hood Canal or at another point along the distribution chain, only describing the illnesses as being "norovirus-like." For now, DOH has closed the area in Hood Canal to commercial and recreational harvest while they research the cause.

Commercial and Recreational Harvesting Closed

on Hood Canal, near Lilliwaup

(from DOH Shellfish Safety Map)

Are they "vibriosis-like" or "norovirus-like" symptoms?
Like vibriosis, caused by the naturally occurring bacterium vibrio parahaemolyticus, symptoms from infection of the unnatural norovirus (aka Norwalk virus) are described in a similar way by DOH. Those are described on the website of the Department of Health as:

Norovirus: The most common symptoms are watery diarrhea, explosive projectile vomiting (that shoots out), and stomach pain.

Vibriosis: Symptoms include diarrhea, abdominal cramps, nausea, vomiting, headache, fever, and chills. The illness is usually mild or moderate and runs its course in 2 to 3 days. In severe cases, hospitalization may be required.  

Norovirus illnesses appeared to have been dropping
Until December's outbreak, norovirus had not been as big of a problem for Washington's shellfish growers. Based on a report from the Center for Science in the Public Interest on norovirus caused by oysters harvested from Washington between 1993 to 2009, since 2007 it has been rare (0 reported in 2007, 2008 and 2009). DOH did report December 2011 illnesses in their March 2012 newsletter but the number was not noted and, until December of 2014, there do not appear to have been any other reported norovirus illnesses traced to Washington.

Until December of 2014
In early December a similar outbreak of illnesses from Washington oysters was confirmed to be norovirus. It is currently believed a leaking septic system was the source, although that could not be confirmed. That harvest area, also in Mason County, was in Hammersley Inlet and like Hood Canal's, was closed.

Will a new plan be needed to address norovirus?
The norovirus-like illness from oysters harvested from Mason County's waters comes at an awkward time as the Department of Health is just now implementing a new training program of 10 classes to try and be proactive in preventing vibriosis, something neither the growers nor DOH had been able to do under the old system. Growers will now be required to monitor water temperatures and, if the water temperature reaches a certain level, will voluntarily cease harvesting. In the past, DOH waited until a certain number of illnesses were traced to a growing area, then retroactively closed the area. Whether relying on the shellfish industry to control vibriosis through the new system will be successful remains to be seen, as does how DOH address the possible growing problem with norovirus in oysters harvested from Washington.