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Oysters – particularly when raw or undercooked – are a common source of norovirus and vibriosis.

Link/share our site at www.kingcounty.gov/oysters


Without laboratory testing, these two illnesses can sometimes be difficult to tell apart, making investigations somewhat more complex. Vibrio is much more likely to occur in the warm summer months. Norovirus tends to be more common during the winter months, but can occur at any time of the year.

In general, raw oysters are most likely to be contaminated in the water before harvesting. Regardless, Public Health Environmental Health Investigators conduct onsite visits for each report of illness associated with raw oyster consumption. This helps control risk factors that may be present that could contribute to the spread of norovirus or Vibrio parahaemolyticus. Risk factors for each illness vary, but may include: oysters from unapproved sources, improper refrigeration of oysters (temperatures must be at or below 41°F), handling of raw foods in such a way to minimize the risk of cross-contamination, ill food workers, and/or improper handwashing practices.

Public Health routinely reports the illnesses to Washington State Department of Health (DOH) Shellfish Program, which is responsible for tracking the harvest locations of the oysters implicated in these illnesses. Multiple illnesses tracked to a common growing area may result in the closure of implicated harvest locations or other enforcement actions. For more information, see the DOH Shellfish Program website.

Norovirus is a highly contagious virus that is frequently spread person-to-person and is often associated with food. Shellfish such as oysters, clams, and mussels are filter feeders which could ingest norovirus if it is present in the water. Though all shellfish can be a source of norovirus infection if consumed raw or undercooked, oysters are much more commonly consumed raw than other shellfish.

Norovirus illness often has a sudden onset of nausea and vomiting and/or watery diarrhea with cramps. A low grade fever, chills, and body aches sometimes occur. Norovirus rarely causes severe complications. Dehydration is the most common complication, particularly among young children and the elderly. No vaccine is available for norovirus.

To prevent norovirus infection:

  1. While cooking shellfish can reduce the risk of norovirus illness, quick steaming or cooking until the shells just open may not be enough to protect against norovirus illness. Norovirus can survive cooking temperatures up to 140°F.
  2. Wash hands, cutting boards, and counters used for shellfish preparation immediately after use to avoid cross contaminating other foods.
  3. Wash hands thoroughly with soap after using the bathroom or changing diapers, and before preparing any food or eating.
  4. Wait at least 48 hours after the last episode of vomiting and/or diarrhea before preparing any food for others.

For more information on norovirus, see:

  1. Norovirus facts, Public Health – Seattle & King County
  2. Norovirus facts, Foodsafety.gov
From the Public Health Insider blog: Love oysters? Pay attention to this warning

Vibrio is a bacteria consisting of multiple species, including Vibrio parahaemolyticus. The bacteria are naturally occurring in marine waters. Eating undercooked or raw shellfish, especially raw oysters, is the main risk factor for acquiring an infection with Vibrio parahaemolyticus. Growth of Vibrio species is amplified during the warmer months and Vibrio levels in shellfish increase during the summer.

To prevent Vibrio infection:

  1. Because raw seafood can be contaminated with Vibrio, always cook shellfish and other seafood thoroughly before eating.
  2. Wash cutting boards and counters used for shellfish preparation immediately after use to avoid cross contaminating other foods.
  3. Wash hands thoroughly with soap after handling raw shellfish.
  4. Stay out of brackish or salt water if you have any wounds (including scrapes and cuts), or cover your wound with waterproof bandage to prevent a skin infection.
  5. Wash wounds and cuts with soap and water if they have been exposed to seawater or raw seafood and raw seafood juices, to prevent a skin infection from Vibrio.

For more information on vibriosis, see:

  1. Vibrio facts, Public Health – Seattle & King County
  2. Vibrio facts, Foodsafety.gov
From the Public Health Insider blog: The raw deal: Why undercooked oysters make you sick

2017 illnesses associated with consumption of raw oysters

Restaurant/venue/vendor Address Meal date Number ill Suspected organism
Elliott's Oyster House* 1201 Alaskan Way Pier 56, Seattle 11/11/2017 13 Norovirus
Elliott's Oyster House 1201 Alaskan Way Pier 56, Seattle 11/10/2017 1 Norovirus
Tankard and Tun^ 1415 1st Ave, Seattle 11/9/2017 1 Vibrio
Taylor Shellfish 1521 Melrose Ave, Seattle 9/16/2017 1 Norovirus or Vibrio
Flying Fish 300 Westlake Ave N, Seattle 9/14/2017 4 Norovirus or Vibrio
Rockcreek 4300 Fremont Ave N, Seattle 9/13/2017 2 Vibrio
Brooklyn 1212 2nd Ave E, Seattle 9/6/2017 1 Norovirus
Coastal Kitchen 429 15th Ave E, Seattle 9/5/2017 2 Norovirus or Vibrio
Coastal Kitchen 429 15th Ave E, Seattle 9/5/2017 2 Norovirus or Vibrio
Coastal Kitchen^ 429 15th Ave E, Seattle 9/5/2017 1 Vibrio
Rockcreek^ 4300 Fremont Ave N, Seattle 8/30/2017 1 Vibrio
Salty's on Alki Beach^ 1936 Harbor Ave SW, Seattle 8/31/2017 1 Vibrio
Habanero Bar & Grill 14830 1st Ave S, Burien 8/28/2017 2 Vibrio
Seastar Restaurant & Raw Bar^ 205 108th Ave NE, Bellevue 8/26/2017 1 Vibrio
McGrath's Fish House 1911 320th St, Federal Way 8/26/2017 1 Vibrio
Blueacre Seafood 1700 7th Ave, Seattle 8/25/2017 1 Vibrio
Pearl Bar & Dining^ 700 Bellevue Way NE #50, Bellevue 8/14/2017 1 Vibrio
2021 2021 7th Ave, Seattle 8/21/2017 1 Vibrio
Elliott's Oyster House^ 1201 Alaskan Way Pier 56, Seattle 8/12/2017 1 Vibrio
Matt's Rotisserie & Oyster Lounge^ 7325 166th Ave Ne Ste. F210, Redmond 8/10/2017 2 Vibrio
Elliott's Oyster House 1201 Alaskan Way Pier 56, Seattle 8/10/2017 1 Vibrio
Pearl Bar & Dining^ 700 Bellevue Way Ne #50, Bellevue 8/8/2017 1 Vibrio
Crow^ 823 5th Ave N, Seattle 8/8/2017 1 Vibrio
Pike Brewing Company and Tankard & Tun 1415 1st Ave, Seattle 8/2/2017 2 Vibrio
Shaker & Spear at Palladian Hotel^ 2000 2nd Ave, Seattle 7/30/2017 1 Vibrio
Walrus & the Carpenter 4743 Ballard Ave NW #1B, Seattle 7/30/2017 1 Vibrio
Taylor Shellfish^ 124 Republican St, Seattle 7/29/2017 1 Vibrio
Elliott's Oyster House 1201 Alaskan Way Pier 56, Seattle 7/23/2017 1 Vibrio
Cutter's Crabhouse^ 2001 Western Ave, Seattle 7/22/2017 1 Vibrio
Elliott's Oyster House^ 1201 Alaskan Way Pier 56, Seattle 7/20/2017 1 Vibrio
Elliott's Oyster House 1201 Alaskan Way Pier 56, Seattle 7/19/2017 3 Vibrio
White Swan Public House^ 1001 Fairview Ave N, Seattle 7/14/2017 1 Vibrio
White Swan Public House 1001 Fairview Ave N, Seattle 7/14/2017 1 Vibrio
Salted Sea 4915 Rainier Ave S, Seattle 7/11/2017 1 Vibrio
Elliott's Oyster House^ 1201 Alaskan Way Pier 56, Seattle 7/9/2017 1 Vibrio
Athenian Seafood Restaurant and Bar^ 1517 Pike Place, Seattle 7/8/2017 1 Vibrio
Salted Sea* 4915 Rainier Ave S, Seattle 7/8/2017 3 Vibrio
Wild Salmon Seafood Market^ 1900 W Nickerson St, Seattle 7/6/2017 4 Vibrio
Salted Sea* 4915 Rainier Ave S, Seattle 7/6/2017 3 Vibrio
Chinooks 1900 W Nickerson St, Seattle 7/6/2017 1 Vibrio
Edgewater Hotel Restaurant (Six Seven)^ 2411 Alaskan Way, Seattle 7/4/2017 1 Vibrio
White Swan Public House* 1001 Fairview Ave N, Seattle 7/3/2017 3 Vibrio
Salted Sea* 4915 Rainier Ave S, Seattle 7/2/2017 2 Vibrio
White Swan Public House* 1001 Fairview Ave N, Seattle 6/30/2017 3 Vibrio
Costco Wholesale #1225 7725 188th Ave NE, Redmond 6/25/2017 1 Vibrio
Matt's Rotisserie & Oyster Lounge^ 7325 166th Ave Ne Ste. F210, Redmond 6/17/2017 1 Vibrio
Salted Sea* 4915 Rainier Ave S, Seattle 6/17/2017 1 Vibrio
Salted Sea*^ 4915 Rainier Ave S, Seattle 6/9/2017 2 Vibrio
Elliott's Oyster House^ 1201 Alaskan Way Pier 56, Seattle 6/6/2017 1 Vibrio
Daniel's Broiler - Lake Union 809 Fairview Pl N, Seattle 4/15/2017 1 Norovirus
Elliott's Oyster House 1201 Alaskan Way Pier 56, Seattle 4/6/2017 2 Norovirus
Sitka and Spruce 1531 Melrose Ave E., #6, Seattle 4/1/2017 2 Norovirus
Elliott's Oyster House 1201 Alaskan Way Pier 56, Seattle 4/1/2017 1 Norovirus
Elliott's Oyster House 1201 Alaskan Way Pier 56, Seattle 3/26/2017 2 Norovirus
Jack's Fish Spot 1514 Pike Place, Site 2, Seattle 3/24/2017 1 Norovirus
Salted Sea 4915 Rainier Ave S, Seattle 3/20/2017 1 Norovirus
Big Fish Grill 984 NE Park Drive, Issaquah 3/20/2017 4 Norovirus
The Walrus and the Carpenter 4743 Ballard Ave NW, Seattle 3/20/2017 2 Norovirus
Chandlers Crab House 901 Fairview Ave N, Seattle 3/12/2017 2 Norovirus
RN74 1433 4th Ave, Seattle 3/10/2017 2 Norovirus
Private party: Taylor Shellfish (oysters from Taylor Shellfish) 130 SE Lynch Rd, Shelton 3/10/2017 15 Norovirus
Taylor Shellfish (restaurant) 1521 Melrose Ave, Seattle 3/10/2017 3 Norovirus
Anchovies and Olives 1550 15th Ave, Seattle 3/4/2017 1 Norovirus
Orfeo 2107 3rd Ave, Seattle 2/28/2017 2 Norovirus
Herb and Bitter 516 Broadway E, Seattle 2/25/2017 2 Norovirus
Anchovies and Olives 1550 15th Ave, Seattle 2/17/2017 2 Norovirus
Girin 501 Stadium Pl S, Seattle 2/17/2017 1 Norovirus
Art of the Table 1054 N. 39th St, Seattle 2/14/2017 2 Norovirus
Bar Melusine 1060 E Union St, Seattle 1/20/2017 2 Norovirus
Taylor Shellfish* 124 Republican S, Seattle 1/10/2017 4 Norovirus
The White Swan Public House 1001 Fairview Ave N, Seattle 1/6/2017 1 Norovirus

*Disclosures posted previously online at: www.kingcounty.gov/outbreak
^Includes at least one ill person with laboratory-confirmed Vibrio parahaemolyticus

Resources

  1. DOH Shellfish Program website

  2. Norovirus
  3. Vibriosis

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