Vibriosis and norovirus associated with consumption of raw oysters
Updated September 22, 2017
In the last two weeks we have seen an increase in reports of ill persons with gastroenteritis symptoms more suggestive of norovirus after eating raw oysters. We have changed this outbreak posting to reflect all reported illness associated with consuming raw oysters, not just Vibrio.
Since our last update on September 11th, seven additional meal parties with either Vibrio-like or Norovirus-like illness have been reported and investigated. Two meal parties had at least one person with lab-confirmed Vibrio parahaemolyticus. This brings the total number of persons known to be ill after consuming raw oysters to 68.
Norovirus symptoms include nausea, vomiting, diarrhea, body aches, chills and sometimes a low-grade fever. Symptoms typically start 1-2 days after exposure and last for about 1-2 days as well. Vibrio parahaemolyticus, on the other hand, typically consists of watery diarrhea, abdominal cramping, and vomiting that usually lasts for 3 days or longer. Both are generally self-limiting illnesses, so many people do not seek health care. Often in norovirus outbreaks no laboratory testing is ever done.
Environmental Health inspectors continue to conduct on site investigations of each facility reported to ensure that there are no factors present that could contribute to the spread of norovirus or Vibrio.
Six additional meal parties with Vibrio-like illness have been reported and investigated since the last update. Three meal parties had at least one person with lab-confirmed Vibrio. This brings the total number of persons known to be ill to 56.
Thirteen additional meal parties with Vibrio-like illness have been reported and investigated since the last update. Ten meal parties had at least one person with lab-confirmed Vibrio. This brings the total number of persons known to be ill to 50.
Four additional meal parties with Vibrio-like illness have been reported and investigated since the last update. One meal party had a lab-confirmed Vibrio case. Two meal parties had meals in early July and were reported to Public Health a month later. This brings the total number of persons known to be ill to 36.
Four additional meal parties with Vibrio-like diarrheal illness (likely Vibrio parahaemolyticus) have been reported and investigated since the initial posting, including two parties with laboratory-confirmed Vibrio cases. This brings the total number of persons known to be ill to 31.
Public Health continues to provide information on the oyster sources to the DOH Shellfish program. One growing area parcel has been temporarily closed as a result of the illness reports.
Note that this investigation into Vibrio illnesses is separate from the more recent investigation announcement, where a Vibrio vulnificus case developed an infection from a wound acquired while handling fish from a live tank at a local supermarket.
Since early June, Public Health has investigated multiple reports of persons ill with watery diarrhea, abdominal cramping, and vomiting – symptoms consistent with vibriosis - after eating raw oysters from one of several restaurants and markets in King County (see table below for meal locations and dates). As many as 25 people may have become ill, though not all were interviewed directly by Public Health.
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.
For each retail/restaurant location reported, Environmental Health inspectors conducted on site investigations to ensure that the oysters were from approved sources, being cold held properly (at refrigeration temperatures at or below 41°F) and handled in such a way to minimize the risk of cross-contaminations (where bacteria from one bad oyster could be spread to a whole batch, or to other foods). The Vibrio bacterium is naturally found in salty, brackish waters where oysters are grown. Therefore, while temperature violations before and after delivery to restaurants can contribute to the growth of Vibrio, the restaurants are not the direct source of Vibrio in oysters.
Vibrio and oysters
The majority of reports that Public Health has been investigating this summer have been for Vibrio-like illness associated with raw oysters. Vibrio species are bacteria that occur naturally in marine waters, where oysters live and are harvested. Eating undercooked or raw shellfish, especially raw oysters in warm-weather months, is the main risk for acquiring vibriosis from infection with Vibrio parahaemolyticus.
Norovirus and oysters
With the recent increase in reports of gastroenteritis symptoms more suggestive of norovirus, we have updated our posting to include this new information. Shellfish such as oysters, clams, and mussels are filter feeders. They 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.
|Taylor Shellfish||1521 Melrose Ave||9/16/2017||1||Norovirus or Vibrio|
|Flying Fish||300 Westlake Ave N||9/14/2017||4||Norovirus or Vibrio|
|Brooklyn||1212 2nd Ave E||9/6/2017||1||Norovirus|
|Coastal Kitchen||429 15th Ave E||9/5/2017||2||Norovirus or Vibrio|
|Coastal Kitchen||429 15th Ave E||9/5/2017||2||Norovirus or Vibrio|
|Coastal Kitchen^||429 15th Ave E||9/5/2017||1||Vibrio|
|Rockcreek^||4300 Fremont Ave N||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|
*Disclosures posted previously online at: www.kingcounty.gov/outbreak
^Includes at least one case with Lab-confirmed Vibrio parahaemolyticus.
Norovirus is a highly contagious virus that is frequently spread person-to-person and is often associated with food. 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:
- 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.
- Wash hands, cutting boards, and counters used for shellfish preparation immediately after use to avoid cross contaminating other foods.
- Wash hands thoroughly with soap after using the bathroom or changing diapers, and before preparing any food or eating.
- 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:
- Norovirus facts, Public Health – Seattle & King County
- Norovirus facts, Foodsafety.gov
- The raw deal: Why undercooked oysters make you sick, Public Health Insider
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 vibriosis from 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:
- Because raw seafood can be contaminated with Vibrio, always cook shellfish and other seafood thoroughly before eating.
- Wash cutting boards and counters used for shellfish preparation immediately after use to avoid cross contaminating other foods.
- Wash hands thoroughly with soap after handling raw shellfish.
- 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.
- 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: