Key Findings:

• A confirmed case for this outbreak was an individual who ate at Sushi Nine between 11/28/23 and the restaurant closing on 12/5/23, reported having symptoms of norovirus (nausea, vomiting, diarrhea, abdominal pain, fever, headaches, body aches) within 3 days of eating at Sushi Nine, and had a laboratory test result that was positive for norovirus.

• A probable case for this outbreak was an individual who ate at Sushi Nine between 11/28/23 and the restaurant closing on 12/5/23, reported having symptoms of norovirus (nausea, vomiting, diarrhea, abdominal pain, fever, headaches, body aches) within 3 days of eating at Sushi Nine but did not have a laboratory test positive for norovirus.

• 263 individuals were investigated during this outbreak. Out of 263:

– 57 were not included in the case counts because their date for eating at Sushi Nine and/or illness onset date were unknown, or their dates were outside of the appropriate range.

– 203 were probable cases.

– 3 were confirmed cases.

• Three days was chosen because the typical incubation period for norovirus is 12 to 48 hours after consumption. Allowing for a third day accounted for anyone who ate or got sick late in the evening, shortly before or after midnight.

• Most commonly occurring symptoms among cases were nausea, vomiting, diarrhea, fever, abdominal pain, headaches, and body aches.

Initial Stages of Investigation

• Around 4 PM on Friday, December 1, 2023, Wake County Environmental Health Services (EHS) received a complaint from a parent regarding their adult child and child’s friend going to Sushi Nine the evening prior (November 30, 2023) and becoming sick overnight with nausea, vomiting, and diarrhea.

• When EHS staff talked to a manager at Sushi Nine shortly after receiving the complaint, the manager reported two other customers had called the restaurant on December 1 also reporting illness. At this time, all customers who had reported illness had consumed the spicy tuna salad, and the manager was concerned about the tuna and discarded all tuna; however, the outbreak continued, and later illness reports came from individuals who ate other menu items that did not contain tuna.

• After first talking with the manager, the restaurant manager interviewed all employees to determine if they were potentially sick when working. Two employees reported being sick after working but had not returned to work at that time since developing symptoms. No employees reported being sick while working. The manager also recalled an incident where a woman and a child used the restrooms on the afternoon of November 30 and left quickly afterwards. Evidence of diarrhea was then found on the walls and floors in two of the three restrooms (the women’s and family ones). Information on how this was cleaned was provided to Environmental Services. This was initially an incident of interest but later determined that it would not account for individuals who had already reported being sick on November 29 and 30.

• Additional complaints were received in the following days by both EHS and the Wake County Health and Human Services Communicable Disease (CD) staff through the foodborne illness web submit form.

• By Monday, December 4, 2023, the count of complaints was up to 11. Wake County EHS and CD staff were reaching out to each individual and interviewing those they got in contact with.

• The first confirmed case had a lab test positive for norovirus collected on December 3, and the second confirmed case had a lab result positive for norovirus on December 4.

• New complaints continued to be reported and on December 5, the restaurant decided to close early after discussions with EHS.

• The restaurant remained closed December 6 and 7 and re-opened on December 8. During this time, they performed deep-cleaning and disinfecting of all areas of the restaurant.

• New complaints continued to be reported during this time from those who ate at Sushi Nine on 11/28 through the closure on 12/5 and developed symptoms of norovirus shortly after.

• The third confirmed case had a positive lab result for norovirus that was collected on December 6.

• The number of complaints grew quickly after WRAL published an initial news story on Thursday, December 7 and when additional articles and news stories were published by other news outlets after that.

• From the start of the outbreak until it was declared over, Wake County staff recorded and interviewed, or attempted to interview, 263 complainants.


Norovirus (GI/GII) was detected in three stool samples through PCR testing. These samples were collected from individuals seeking healthcare at emergency departments, and the labs were processed by those hospital systems.

Investigation Findings

Following the identification or notification of potential cases, Wake County CD nurses conducted inquiries with those individuals regarding when they visited Sushi Nine, when they developed symptoms, what they ate during their visit, other aspects of their visit to Sushi Nine, their symptoms, and if they have sought healthcare. Copies of the three lab results were uploaded into the outbreak’s event ID in the North Carolina Electronic Disease Surveillance System (NCEDSS) but no IDs were created for the cases (norovirus, by law, is not a reportable disease in North Carolina).

The Wake County epidemiology team examined the potential cases linked to the outbreak and analyzed the menu items reported to have been consumed at Sushi Nine by the individuals affected. A list of the most frequently reported menu items is included at the end of this report in Appendix A. Most of the items on the restaurant’s menu were reported as consumed by an affected individual at least once. Additionally, no common ingredient was found. A large portion of the most frequently reported menu items consumed contained tuna and/or avocado but many didn’t include either of those items. Wake County investigated all potential sources of exposure. The investigation did not point to a specific source of contamination, which is common in norovirus investigations. The epidemiology team periodically analyzed the available data while the outbreak was still on-going to provide summaries for those involved from Wake County, in addition to providing this final analysis.

Food Safety Investigation

Wake County Environmental Health Services (EHS) received the first complaint related to this outbreak shortly after 4 PM on Friday 12/1/2023. The following is a summary of EHS’ investigation and visits to the restaurant.

Friday, December 1, 2023 (after receiving initial complaint):

• EHS spoke with a manager of the restaurant regarding employee health, bare-hand contact, handwashing, other complaints the restaurant had received, details of the complaint (food consumed, symptoms, date and time of consumption).

• The manager thought the trimmings from the spicy tuna salad could be a suspect food, so the manager discarded all opened tuna and began using new packages of tuna for the sashimi and spicy tuna salad.

• EHS and the manager also discussed employee illness reporting requirements, handwashing, glove use, and more.

Monday, December 4, 2023:

• Complaints that were received by EHS over the weekend were processed and EHS contacted complainants to determine information such as when they ate at Sushi Nine, what foods were consumed, when their symptoms began, and other relevant information.

• EHS informed Wake County Communicable Disease (CD) staff of the complaints received by EHS and sent information from complainant interviews to the restaurant manager and CD staff.

• Sushi Nine management implemented a temporary policy to discard all leftovers at the end of each day’s operation as an extra precaution.

Tuesday, December 5, 2023:

• Complaints continued to be received by Wake County EHS and CD staff.

• An EHS staff member visited the restaurant reviewed the norovirus sections of employee health policy and norovirus event clean-up guidance with staff.

• The manager interviewed employees per employee health policy, and two employees reported feeling ill with similar symptoms as the complainants after working shifts at Sushi Nine (but as of 12/5/2023 had not worked since becoming ill on 11/30 and either 12/2 or 12/3)

• The manager informed EHS that there was a customer diarrhea event on 11/30/23 at 2:30pm in 2 customer restrooms (described in more detail in Initial Stages of the Investigation section).

• A letter from Wake County’s Environmental Health and Safety manager was emailed to the restaurant manager to discuss closure of the restaurant. The restaurant voluntarily closed early at 8:20 PM on 12/5/2023 to perform detailed cleaning and disinfecting.

Wednesday, December 6, 2023:

• EHS informed the restaurant manager that complaints of customers who ate on 12/4/2023 (Monday) were being received.

• The manager sent videos of major facility cleaning taking place, including moving the cookline equipment, clearing the serving areas, disinfection with chlorine, and more. EHS staff communicated with the manager about where and how to clean and disinfect.

Thursday, December 7, 2023:

• EHS staff visited the restaurant to verify cleaning and disinfection was performed per the guidance provided by EHS, as well as meet with the restaurant manager.

• Additional guidance and instruction was given on employee health and handwashing to the employees through materials translated from English to Spanish. However, four languages are spoken by employees- Thai, Spanish, Korean, and English.

Friday, December 8, 2023:

• The restaurant re-opened on 12/8/2023. 

Monday, December 11 to Friday, December 15, 2023:

• EHS staff visited the restaurant again on Monday 12/11; this visit entailed meeting with the restaurant operators and providing instruction on handwashing, norovirus transfer, and diarrhea and vomit cleanup procedures. It was noted that chlorine disinfectant is being used on dining room surfaces each night.

• On 12/12, EHS staff updated the restaurant manager on the actions CD and EHS staff had taken, including the continuing investigation of complaints that had eaten at the restaurant before the closure on 12/5.

• On 12/14, EHS staff visits the restaurant; during this visit, the staff member communicated with the manager on approved disinfectants, observed proper handwashing practices and disinfectant use, and discussed relocating the handwash soap dispensers to facilitate handwashing in approved locations.

• On 12/15, EHS staff informed the restaurant manager that the outbreak was declared over on 12/11 due to 2 incubation periods passing without new cases. Additionally, EHS staff continued discussion with the manager on the importance of handwashing and adherence to the employee health policy took place as well.


The last reported case in this outbreak had a symptom onset date of 12/7/2023. The outbreak was declared over as of 12/11/2023 because twice the incubation period for norovirus is 96 hours (4 days). There have been no additional cases identified since that time. Norovirus is a highly contagious virus usually transmitted from having direct contact with someone infected, consuming contaminated food or water, or touching contaminated surfaces and then putting your unwashed hands in your mouth. While many potential sources were identified during the investigation of this outbreak, no definitive source was determined.

What worked well?

• Collaboration between Wake County’s CD, Epidemiology, and EHS programs, as well as NCDHHS.

• Thoroughly investigating the implicated facility promptly to inform and educate them and prevent future infections.

• The facility voluntarily closing early on 12/5/2023 and remaining closed to perform thorough cleaning and disinfection until 12/8/2023. No cases reported eating at Sushi Nine since the re-opening on 12/8/2023.


• Difficulty identifying an exact cause (either ill staff or food source).

• Lack of complete information for possible cases; this was due to several reasons, but some included one person reporting for a group and not having contact information for the additional individuals and/or the additional individuals not answering or returning calls.

• Individuals having difficulty recalling what they ate; some individuals could not recall the menu item names and listed one of the ingredients in it but not enough to narrow down to the specific item (an example would be saying they had one of the sushi rolls that has salmon and multiple rolls on the menu contain salmon).


• Wash hands often with soap and water for at least 20 seconds. Hand sanitizer does not work well against norovirus.

• Handle and prepare food safely by washing fruits and vegetables well, cooking oysters or shellfish thoroughly and routinely cleaning and sanitizing kitchen utensils, counters, and surfaces.

• Avoid preparing or handling food when sick; wait at least two days after symptoms subside before preparing food or providing healthcare to others.

• Clean and disinfect surfaces often, especially when someone has been sick; wash clothes or linens immediately if someone has been sick on them.