By: James Peacock

In an expansion of the individual investigations that the Seattle & King County Health Department announced last week, health officials have begun an investigation into Vibrio cases at quite a few more restaurants. Both outbreak investigations from last week are both included in this larger outbreak investigation. At the time of their individual announcements, there had been three people sickened after eating at the Salted Sea and six people sickened after eating at the White Swan. Now, five other restaurants have been added to the Vibrio investigation, because people have reported illnesses occurring after eating oysters there. Many other cases were added to the number of people sickened by oysters at the Salted Sea. There have now been at least 25 reports of Vibrio poisoning since early June. Not all of the people sickened in the outbreak were interviewed directly by the health department. The table provided below lists the cases of illness, what date the exposure to Vibrio bacteria occurred, the restaurant or store where the contaminated oysters were sold, and the address of those locations.

The Investigation

Investigators reported each case of illness to the Washington State Department of Health’s Shellfish Program. The Shellfish Program tracks the harvest locations of foodborne illness causing oysters. If a harvest area begins to cause a series of foodborne illnesses, they will be closed or subject to other enforcement acts. The investigators from the Shellfish Program have not yet been able to narrow down what harvesting area supplied the contaminated oysters. As the investigation progresses, though, they may discover a source. The investigators from the Seattle & King County Health Department have visited all of the restaurants implicated in the outbreak. They concluded that “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.”

Restaurant/Store Address Date of Meal Cases of Illness
Elliott’s Oyster House 1201 Alaskan Way Pier 56, Seattle 6/6/2017 1
Salted Sea 4915 Rainier Ave S, Seattle 6/9/2017 2
6/17/2017 1
7/2/2017 2
7/6/2017 3
7/8/2017 3
Matt’s Rotisserie & Oyster Lounge 7325 116th Ave Ne Ste. F210, Redmond 6/17/2017 1
Costco Wholesale #1225 7725 188th Ave Ne, Redmond 6/25/2017 1
The White Swan Public House 1001 Fairview Ave N, Seattle 6/30/2017 3
7/3/2017 3
Chinooks 1900 W Nickerson St, Seattle 7/6/2017 1
Wild Salmon Seafood Market 1900 W Nickerson St, Seattle 7/6/2017 4

The Spring 2017 Norovirus Outbreak

Oysters are a very common source of foodborne illness outbreaks, as they are often served raw. Washington State is also not unfamiliar with oyster-related outbreaks. Earlier this year, there was an outbreak of norovirus linked to raw oysters sold across the state. As many as 55 people may have been sickened in this outbreak across the state. People sickened in that outbreak ate at various restaurants, all of which had common suppliers. Twenty-two different restaurants were tied to the outbreak. Interestingly, there have been a few restaurants connected to both outbreaks. Both the Salted Sea and the White Swan Public House had one reported illness, while five people were reported to be ill after eating at Elliott’s Oyster House. The investigation traced the oysters back all the way to the growing areas from which they were harvested from. Health officials then closed these growing areas, which supplied oysters to more than 30 different companies.

Vibriosis

There is a large number of different Vibrio species in the world, but only about a dozen or so cause illness in humans. The more common pathogenic species are Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio alginolyticus. Of these, Vibrio parahaemolyticus is the most commonly reported, causing about 45,000 cases of illness per year. Vibrio is a bacterium that is commonly found in tropical and temperate areas. It requires a very specific set of environmental circumstances in order to survive and grow. Vibrio bacteria optimally grow between 68 and 95 degrees Fahrenheit. The bacteria are capable of growing in temperatures up to 105 degrees. When the temperature falls below 50 degrees, though, Vibrio is gradually inactivated. This makes Vibrio highly susceptible to refrigeration and freezing. Vibrio also requires a salty environment in order to grow, preferring around two percent of the composition of water to be NaCl. Oysters, with a salt content of about 23 parts per trillion, are frequently the vehicle for Vibrio infections. The bacteria die almost immediately in fresh water. Other vulnerabilities associated with Vibrio bacteria include low pH and thorough cooking. The FDA recommends cooking seafood to an internal temperature of 145 degrees Fahrenheit. Most infections come from raw foods, with the vast majority of infections being caused by oysters. Finfish, squid, octopus, lobster, shrimp, crab, and clams have all also been linked to Vibrio infections in the past. Vibrio infections are common in Asian countries and tend to occur in the summer months when the water is warmer.

The CDC estimates that there are about 80,000 cases of Vibrio poisoning per year. The majority of these cases, about 19 out of 20, are not reported. Around 14 percent of Vibrio cases are not foodborne.  Vibrio infections cause around 500 hospitalizations and 100 deaths per year. The CDC estimates that about 100 million bacterial cells are required to cause a case of foodborne illness. The incubation period for Vibrio is between 4 and 90 hours after exposure. The average incubation time for a Vibrio infection is 17 hours. When a Vibrio infection presents symptoms, potentially bloody diarrhea, nausea, abdominal cramping, fever, and vomiting are all commonly seen. A case of Vibrio poisoning will typically last between 2 and 6 days and is fairly self-limiting. Those with diabetes, liver disease, kidney disease, cancer, AIDS, or compromised immune systems are at an increased risk of contracting a serious case of Vibrio poisoning. People with those risk factors are also more susceptible to developing septicemia, a potential complication. This blood infection can be very serious and is fatal between 20 and 30 percent of the time. If you or a loved one begins to show the symptoms of Vibrio poisoning, contact a medical professional.

Sources:

https://www.cdc.gov/vibrio/index.html

http://www.kingcounty.gov/depts/health/communicable-diseases/disease-control/outbreak/vibriosis-oysters.aspx

http://www.kingcounty.gov/depts/health/communicable-diseases/disease-control/outbreak/oysters.aspx