The San Francisco Department of Public Health (SFDPH) has released its draft report on the E. coli O157:H7 outbreak at the Burma Superstar restaurant in that city in August 2013. Eight cases of lab-conformed E. coli infections in unrelated San Francisco residents were tested with PFGE, to identify the outbreak strain of the bacteria.
SFDPH interviewed case-patients with a detailed questionnaire, which identified a common restaurant: the Burma Superstar. Patients visited the restaurant on August 16 and 17, 2013. A total of 22 confirmed and probable case-patients were identified. Thirteen of those patients met the suspect case definition. Initially, investigators looked at a garlic noodle dish, but the specific ingredient that caused the infections was not identified.
Illness onset dates ranged from August 18 to August 24, 2013. The peak of illness corresponds with the typical incubation period for E. coli following exposure on August 16 or 17. The median age of patients was 29 years; 55% were female. Seven people were hospitalized as a result of their infections, and four developed hemolytic uremic syndrome (HUS).
The environmental investigation found hand washing violations and potential cross-contamination. But no food handlers were ill. However, since testing occurred two weeks after the exposure date, an employee who was ill at the time of infection or was shedding bacteria at that time could have recovered by the time they were tested.
The routes of transmission could have been cross-contamination of food at the restaurant, or from food purchased from a wholesale food facility. The report concludes that the outbreak was “self-limited”. The Burma Superstar has made corrections to violations found during the investigation.
