Category Archives: norovirus

Shopping Bag Norovirus

Outbreak: Reusable Shopping Bag
Product: Reusable Shopping Bag
Investigation Start Date: 10/13/2010
Location: Single County
Etiology: Norovirus
Earliest known case onset date: 10/10/2010
Latest case onset date: 10/12/2010
Confirmed / Presumptive Case Counts: 7 / 5
Positive Samples: 1
Outbreak Summary:
Health officials made a rare discovery with this outbreak by identifying a reusable shopping bag as the vehicle for norovirus investigation. The reusable shopping bag was stored in a bathroom used by the index case during her illness onset. The bag contained cookies, chips and other food items that were eaten by tournament attendees who subsequently became ill.

On October 13, 2010, the Washington County (Oregon) Health Department was notified by epidemiologists from the Washington State Department of Health (WSDH) and Public Health—Seattle & King County (PHSKC) about an outbreak of gastroenteritis affecting members of an Oregon soccer team.
The soccer team had arrived in Redmond, Washington, on Friday, October 8; its members ate in restaurants around town and also consumed homemade items that they had brought with them.

Early the morning of Sunday, October 10, one girl became ill with vomiting and diarrhea and was driven home that day by one of the parent chaperones. A fellow team member, unaware of her teammate’s illness, went into the vacated room and found a reusable plastic grocery bag, containing lunch items, which was stored on the floor of the bathroom.

On Tuesday, October 12, other team members and chaperones became ill, and one of the parents notified PHSKC.

While epidemiologists of WSHD and PHSKC canvassed tournament organizers about any similar reports from other teams, Oregon epidemiologists obtained a team roster and chaperone list. Twenty-one interviews were conducted over the phone or in person at a team practice on Thursday, October 14. One healthy person refused the interview. One ill person was excluded from analysis due to direct exposure to the index case and her vomiting.

Cases were defined as group members who developed vomiting or diarrhea (≥3 loose stools within a 24-hour period) during October 9–13. The follow-up questionnaire specifically targeted meals and all reported food exposures on Friday, Saturday and Sunday, October 9–11. Stool specimens were solicited from persons who had been ill. A reusable grocery bag was tested for norovirus by swabbing small patches of the bag’s surface. Swabs of the surface of the reusable grocery bag were tested for norovirus by real-time, quantitative reverse-transcription polymerase chain reaction (RT-qPCR).

Nine primary and five secondary cases were identified. The noroviral etiology and tight clustering of the Tuesday, October 12, case onsets suggested a common exposure on Sunday afternoon—most likely lunch or something at stopover on the drive home. In the initial cohort analysis, only eating cookies from an unopened package on Sunday at lunch was significantly associated with illness, with 3 of 7 cases consuming and none of 12 healthy cohort members exposed (risk difference [RD] 0.750; 95% CI 0.24–0.91; P = .01). After cases were re-interviewed with the focused questionnaire, investigators learned that the packaged cookies, packaged chips, and fresh grapes had been stored together in a reusable plastic shopping bag with an open top. Further, said shopping bag had been stored in the hotel bathroom where Case 1 had been vomiting throughout the night. Investigators then created a composite variable to include all three items in the bag. All 7 cases but only 4 of 12 healthy cohort members had consumed at least one of the 3 items in the bag (RD 0.636; 95% CI, 0.32–0.87; P < .01; see the published journal article for further analysis detail).

Norovirus genotype GII.2 sequence was detected by RT-qPCR in all 3 stool specimens collected from cases and in swabs of the reusable plastic shopping bag.

Lessons learned & historical significance
This outbreak highlights the risk of acquiring noroviral gastroenteritis from a fomes, the surface of which can be contaminated when left in an enclosed environment with someone who is vomiting. Any surface—not just a visibly soiled one—exposed to an ill person should be fully disinfected. Food and drink should not be stored in toileting areas; anything stored in areas where someone has vomited should never be consumed.
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Diaper Changing Station Norovirus

Outbreak: Diaper Changing Station Norovirus
Product: Diaper Changing Station
Investigation Start Date: 5/16/2012
Location: Washington County, OR
Etiology: Norovirus
Earliest known case onset date: 5/15/2012
Latest case onset date: 5/15/2012
Confirmed / Presumptive Case Counts: 12 / 4
Positive Samples: 1
Hospitalizations: 0
Deaths: 0
Outbreak Summary:
This outbreak initially appeared to be a standard foodborne point-source outbreak from a restaurant with known previous critical violations. However, upon extensive interviewing, it transpired that a toddler with explosive diarrhea and the associated contaminated surfaces were the source of the outbreak.

On May 16, 2012, a local auto dealership called the Washington County (Oregon) Health Department to report a potential foodborne illness outbreak among employees who had attended a staff meeting on May 13. The meeting was held in an open space off the showroom floor. Submarine sandwiches, chips, and condiments from a nearby fast-food restaurant had been provided to attendees.

Environmental health staff conducted an onsite environmental inspection of the restaurant and its operations. Food handlers and restaurant managers reported no recent gastrointestinal illness (within previous 2 weeks) was reported by food handlers or restaurant managers. No other patrons had complained. The restaurant was cited for 2 violations defined by environmental health staff as critical: presence of potentially hazardous food not maintained at proper hot or cold holding temperatures and presence of open beverages on the food preparation table. During interviews with dealership employees, one recalled that a customer with a sick child had used the diaper-changing station in the women’s restroom before the lunch. When the woman and toddler left, the restroom was a mess. The employee cleaned it up as best she could with dry paper towels. She didn’t wear gloves or use bleach but did wash her hands. She left the restroom, opened the dealership’s front door for another employee carrying the food and was the first to take a sandwich from the platter.

Oregon epidemiologists conducted a retrospective cohort study among meeting attendees, using a standard questionnaire to ask about food, environmental exposures, and any history of illness. Cases were defined as meeting attendees who developed vomiting or diarrhea (defined as ≥3 loose stools within a 24-hour period) within 72 hours after the meeting. Environmental health staff evaluated the operations of the restaurant that provided the food, with particular attention to hand washing, food preparation practices, and recent employee illness. Stool specimens were solicited from ill persons and tested for norovirus. Epidemiologists collected environmental samples for norovirus testing from the diaper-changing station at the auto dealership and from a convenience sample of similar diaper-changing stations in public restrooms throughout Washington County.

Stool specimens from 2 employees and the toddler—who was located through auto sales records—were positive for norovirus (genotype GII.6.C) with indistinguishable sequences. According to the mother, the child had been ill for 1 day before the visit to the auto dealership. Although the dealership diaper changing station had reportedly been routinely cleaned twice by a professional janitorial service, using quaternary ammonium disinfectants, we observed brown matter inside and underneath the changing station. Swabs of the brown matter on the changing station were positive for norovirus genotype GII, although the samples did not amplify in viral capsid coding regions C or D, rendering sequencing impossible.

To assess the prevalence of norovirus on diaper-changing stations in Washington County, epidemiologists tested a convenience sample of 14 stations in various restroom locations: 1 restaurant, 3 parks, 3 grocery stores, 1 gas station, 2 shopping malls, 1 aquatic center, 2 libraries, and 1 public health clinic. Eight (57%) of 14 stations had visible brown discoloration on the underside of the fold-down hinge or bed area. All 14 dispensers for disposable bed liners were empty. Norovirus was not detected in swabs of any of the diaper-changing stations other than that the auto dealership.

Lessons learned & historical significance
This outbreak initially appeared as a standard foodborne point-source outbreak from a restaurant with known previous critical violations. However, extensive interviewing revealed that a toddler with explosive diarrhea, and the associated contaminated surfaces, were the source of the outbreak. This outbreak confirms the ability of fomites to transmit norovirus, and the importance of reserving judgment regarding potential foodborne transmission and of considering environmental investigation as a key part of investigating outbreaks of enteric disease.
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Frozen Oysters

Outbreak: Frozen Oysters
Product: Frozen Oysters
Investigation Start Date: 11/22/2006
Location: Marion County, OR
Etiology: Norovirus GI
Earliest known case onset date: 11/15/2006
Latest case onset date: 11/17/2006
Confirmed / Presumptive Case Counts: 2 / 11
Positive Samples (Food): 1
Outbreak Summary:
A rapid investigation of a Norovirus outbreak implicated commercially frozen oysters on the half shell that were thawed and served raw. Over 25,000 pounds of product from the same lot was embargoed by the FDA, which was then considering further restrictions on this type of product, which had been imported from Korea.

On November 22, 2006, an infection control nurse notified the Marion County Health department about acute gastroenteritis among persons who attended a reception at a medical facility on November 16, 2006, and began at 6:00pm. The county asked the state health department to join the outbreak investigation.

After interviewing the caterer, organizers, and several attendees, we modified a questionnaire template to reflect potential exposures. This questionnaire was used in a retrospective cohort study among reception attendees identified from a ticket list of approximately 200 persons. The epidemiologists were able to sample 66 attendees from 50 households.

Ten persons met the case definitions of acute gastroenteritis, 53 had no symptoms, and three were excluded due to minor symptoms. Acute gastroenteritis cases were defined as reported vomiting or ≥ 3 loose stools within a 24 hour period within 18–72 hours of the event.

The median incubation period was 36 hours (range, 31–63 hours). Two stool samples were obtained, and both tested positive for norovirus (1 positive for genogroup II and 1 positive for both I and II). Illness was associated with consumption of raw oyster on the half shell, which was reported by 9 of the 10 cases (RR 11.8; 95%CI 2.8–50; p=0.0001). No other foods were associated with illness.

The oysters had been individually quick frozen on the half shell and packed loosely in cartons after being harvested in South Korea by growers approved by the US Food and Drug Administration. The oysters are pressure-treated to crack the shell, and then blast-frozen on the half shell in trays with a plastic seal over each tray. These oysters were packed in cardboard cartons—144 oysters with a net weight of 6-kg per box. For the reception, a single 6-kg box of oysters was thawed and served raw. The box was from a shipment of 2,200 boxes legally imported in October 2006. Boxes from the same shipment had been distributed to 5 states. No similar outbreaks were reported in the other states that got oysters from the same lot, though case-finding efforts vary. FDA tested oysters from the implicated lot and found Norovirus.

Lessons learned/historical significance
Although most reported foodborne norovirus outbreaks may stem from ill food handlers, it is important to rule out contaminated foods as the source of illness.

Because thorough outbreak investigations are time-consuming and gastroenteritis outbreaks are common, resource considerations often affect decisions about how intensively to pursue investigations. Oregon’s use of integrated questionnaire, data entry, and analysis templates facilitated a quick and successful response to the outbreak described here. Questionnaire design, interviews, data entry, and analysis were completed within 6 hours of the initial report, and distributors and regulatory agencies quickly recalled other oysters from the same source, probably preventing additional illnesses. Widespread use of such templates may increase the number of outbreaks that could be investigated thoroughly.
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Cholo’s Mexican Restaurant, Oahu

Outbreak: Oahu Norovirus
Product: Cholo's Mexican Restaurant
Location: North Shore of Oahu, Hawaii
Etiology: Norovirus
Confirmed / Presumptive Case Counts: 10 / 80
Earliest known case onset date: 04/08/2011
Latest case onset date: 04/11/2011
Outbreak Summary
Still need an outbreak summary.
Cholo’s is a popular (and generally good) Mexican restaurant up on the North Shore of Oahu, the most populous island in Hawaii.

Unfortunately for them, though, they apparently had some workers who had norovirus infection and proceeded to contaminate the food they prepared.

The outbreak was picked up via participants of a century (bike) ride who ate at the restaurant after their event, got sick, and reported their illness to us.

We subsequently identified at least 80 individuals who had consumed food at the restaurant from April 8–10, 2011. Stools from about 10 of them were positive for norovirus.

The restaurant engaged in extensive cleaning and education of their workers and was able to continue operations afterward.
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