Thirteen of the cases reported between November and December had also eaten at the Twisted Fork; however, six cases had a common exposure to food served at different Reno area restaurant, Heritage Restaurant, located within the Whitney Peak Hotel. Contra Costa County (California) Public Health notified WCHD that two Contra Cost county residents were diagnosed with E. coli O157 and they had also eaten at the Heritage Restaurant during their exposure period. All laboratory-confirmed cases had an indistinguishable pulsed field gel electrophoresis (PFGE) pattern combination designated as EXHX01.0047/EXHA26.0015.
WCHD obtained a list of ingredients for all menu items from the Twisted Fork, some of which were dessert items purchased from Reno Provisions. A new E. coli case was reported to WCHD on November 17, 2015. This case patient had eaten dessert at Heritage Restaurant and had no meals at the Twisted Fork. WCHD determined that all desserts at Heritage Restaurant were made by Reno Provisions.
On November 17, WCHD environmental health staff collected food samples and environmental swabs from the Twisted Fork, Heritage Restaurant, and Reno Provisions. The samples were tested by the Nevada State Public Health Laboratory. Two samples of the chocolate mousse/marquis dessert were positive for the outbreak strain (EXHX01.0047/EXHA26.0015) of E. coli O157. A sample of chocolate marquise collected from the reach-in cooler at the Twisted Fork was positive (Sample ID # CL2015-00021043). A sample of chocolate marquise collected from the walk-in freezer at Reno Provisions was also positive for the outbreak strain (Sample ID# CL2015-00021048). No other foods or environmental swabs were positive for Shiga Toxin E. coli.
While on site at Reno Provisions, WCHD environmental health staff learned that the company’s meat department had used the Hobart mixer in the bakery area to mix raw pork sausage. This same Hobart mixer was used to make the chocolate mousse/marquise dessert for both the Twisted Fork and the Heritage Restaurant. Environmental surface swabs from the Hobart mixer and butcher shop area as well as a sample of raw pork were obtained on November 19. All samples collected on the 19th were negative for Shiga Toxin E. coli. Although the exact method of contamination of the chocolate mousse/marquise dessert could not be verified, it is likely that the dessert became contaminated through cross contamination.
The final case count for this outbreak was twenty-five. Sixteen patients were laboratory confirmed and nine were probable cases based upon symptoms and exposure history. Of the confirmed and probable cases, eighteen were patrons of the Twisted Fork, five were patrons of Heritage Restaurant, and two were employees of the Twisted Fork. Fourteen cases were female and eleven were male. The median age was thirty-four (range 6-82 years). Illness onset dates ranged from October 4 to November 13, 2015 with a median incubation period of 3.5 days (range 1-7). Of the nineteen cases who sought medical care, eleven were hospitalized and five developed Hemolytic Uremic Syndrome (HUS). No fatalities were reported.
The chocolate mousse cake manufactured by Reno Provisions and distributed to the Twisted Fork and to Heritage Restaurant was the definitive cause of this outbreak. All sixteen laboratory-confirmed cases had an exposure to one of the two restaurants and also recalled consuming the chocolate mousse/marquis cake. All nine probable cases had exposure to either the Twisted Fork or Heritage Restaurant. Of the nine probable cases, seven recalled consuming the chocolate mousse/marquis cake. As a result of the outbreak, Reno Provisions implemented a number of recommendations for controlling disease and preventing exposure to foodborne pathogens.
Marler Clark represented 9 people affected by the outbreak, achieving settlements covering medical expenses, wage loss, and pain and suffering.