A total of 22 people in San Francisco fell ill in August in an E. coli O157:H7 outbreak linked to Burma Superstar, a restaurant in the Richmond neighborhood, according to an outbreak report released Monday by the San Francisco Department of Public Health. The department first received eight reports of E. coli illness between Aug. 23 and 26 – an unusually high number compared to the typical rate of fewer than one case per month. The cases were dispersed throughout the city, but suggested a moderate-to-high socioeconomic status. Patients also tended to be younger, salad-eating, local-market shopper types in comparison to the average city resident. By Aug. 30, health department questionnaires identified a common exposure among the patients: eating at Burma Superstar on Aug. 16 and 17. Burma Superstar’s owners closed the restaurant over Labor Day weekend to allow investigators time to determine the exact cause of the outbreak. Investigators could not pinpoint an exact source of the contamination, but they were able to make environmental health recommendations such as improving employee handwashing and food handling. Seven patients were hospitalized due to their infections, with four of those developing hemolytic uremic syndrome, a potentially fatal kidney disease associated with severe E. coli infections. No one died. All 31 employees of the restaurant were stool culture tested for E. coli and results came back negative. However, testing of employees took place approximately two weeks after the onset of the outbreak, and any affected employees might have recovered from their illness by the time the samples were collected. According to the health department, potential routes of transmission included cross-contamination of food at the restaurant or at a wholesale food supplier, but food tracebacks could not lead investigators to a conclusion. This was the first outbreak incident in the restaurant’s 17 years of business. Despite the outbreak, Burma Superstar was placed on the coveted Michelin Bib Gourmand list for 2014, an honor given to high-scoring “value” restaurants serving two courses of dinner and wine for $40 or less. The restaurant also made the list in 2013. The health department considers the outbreak investigation a success, stating that it may serve as a model for future investigations. The case may have been helped by the prompt issuing of health alerts, as well as extensive cooperation on the part of Burma Superstar during all parts of the investigation. “Although the outbreak came to public health attention rapidly, and epidemiologic and environmental investigations were initiated promptly, the resulting control measures are not likely to have influenced the course of the outbreak,” the health department’s report stated. “Nonetheless, the Environmental Health investigation of Burma Superstar revealed several violations that may have contributed to the outbreak, and their correction may lead to prevention of future food-borne illnesses due to cross-contamination and other factors. “