Public Health, Salmonella

Salmonella outbreak linked to Issaquah Costco deli

Salmonella associated with the service deli at Costco Wholesale Warehouse in Issaquah


From Public Health – Seattle & King County

Public Health is investigating an outbreak of salmonellosis associated with food prepared in the service deli at the Costco Wholesale Warehouse in Issaquah. The service deli prepares and sells ready-to-eat foods, including rotisserie chicken, pork ribs, sandwiches, wraps, macaroni and cheese, poke, cilantro lime shrimp, and shrimp cocktail.

At this time, the source of the illnesses has not been identified. Everyone who reported illness has recovered.


  • Cases: 7
  • Hospitalizations: 1
  • Deaths: 0
  • Status: Investigation is ongoing
  • Location: Costco Wholesale Warehouse service deli, 1801 10th Ave NW, Issaquah, WA 98027
  • Prior food safety inspections and current rating: GOOD


Since August 28, 2017, we have learned of seven King County residents who tested positive for Salmonella I,4,[5], 12:i:- infections. DNA fingerprinting was performed on the Salmonella bacteria from the seven people who got sick and was identical for all cases, suggesting a common source of infection.

Illness onsets occurred sporadically during August 28, 2017–July 13, 2018, and a common epidemiological link among all cases was not established until August 2018; no single food item prepared by the service deli has been identified as the source of the illnesses.

All seven people who got sick shopped at the Costco Wholesale Warehouse in Issaquah; five bought ready-to-eat food from the service deli, food purchase history cannot be verified for one person, and one was an employee at the Costco service deli. There is no evidence to indicate that the service deli employee is the source of the outbreak.

In September, an eighth person with Salmonella I,4,[5], 12:i:- infection was reported. However, this infection was caused by a Salmonella strain with a different DNA fingerprint that does not appear to be closely related to the other seven people who got sick, suggesting that this case is not related to the outbreak.

Public Health actions

As part of the Public Health investigation, Environmental Health investigators visited Costco Wholesale Warehouse in Issaquah on August 7, 2018. Investigators identified potential risk factors for cross contamination and spread of bacteria, including inconsistent handwashing practices and improper cleaning and sanitizing of surfaces that touch foods.

Corrective actions were addressed with Costco Issaquah management, including food handling procedure changes, retraining employees on food safety practices, and documenting appropriate cleaning and sanitizing practices.

Investigators re-visited the service deli on August 30, 2018, to ensure corrective actions had been addressed. Investigators again identified concerns for inconsistent handwashing practices and improper cleaning and sanitizing of surfaces that touch foods. Corrective actions were addressed with Costco Issaquah management.

On September 19, 2018, Environmental Health investigators asked Costco Issaquah’s service deli to temporarily stop preparing ready-to-eat foods that would not be cooked further by the customer in order to reevaluate food handling practices and procedures.

On September 20, 2018, investigators visited the facility and identified further areas for improvement to limit cross contamination. The facility was instructed to provide additional food handling training to service deli employees to minimize the risk of cross contamination, such as hand washing and sanitation of surfaces where foods are prepared and stored. In addition, completion of a deep cleaning and disinfection of the service deli was required before resuming preparing and selling of ready-to-eat foods.

The investigators re-visited the service deli on September 21, 2018, to confirm the facility had completed a thorough cleaning and disinfection and that a plan for further training and procedure changes had been initiated. Costco Issaquah provided sufficient evidence of a thorough disinfection and corrective actions so the service deli was allowed to resume their normal food preparation operations. Another follow-up visit will occur within 14 days to ensure all corrective actions have been completed.

Environmental testing

Raw poultry and environmental samples collected in the service deli on August 7, 2018, tested negative for Salmonella I,4,[5], 12:i:- at the Washington State Public Health Laboratory.

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