Officials with the Vermont Department of Health say that two more cases of Shiga toxin-producing E. coli (STEC) have been linked to ground beef that was served at Worthy Burger in South Royalton, VT. That brings the outbreak total to six confirmed and three probable cases. According to a Wednesday, Sept. 30, news report, state health inspectors found the DNA of Shiga toxin in unopened packaged beef at Worthy Burger and believe that undercooked hamburgers were the source of the contamination. Bradley Tompkins, a health surveillance epidemiologist with the Vermont Department of Health, said all those sickened have recovered, although to varying degrees. Eight of the nine people ate ground beef at Worthy Burger between the end of August and the middle of September, when department investigators inspected the restaurant, recommended some changes, and took samples of ground beef and lettuce to test. Tompkins said the lettuce tested negative, but DNA for Shiga toxin was found in the ground beef. However, an effort to grow the E. coli in the lab resulted in a slightly different strain than the one found in those sickened. “It’s certainly not conclusive that it did come from the ground beef, (but) based on the interviews that were done with the patients and that we found the E. coli and the Shiga toxins … we do believe the outbreak was caused by the ground beef that was being undercooked from the restaurant,” Tompkins said. The USDA’s Food Safety and Inspection Service (FSIS) said the situation was still being investigated and the ground beef traced back to where it came from. The restaurant closed on Sept. 17 for five days to make some changes and has switched to using ground beef from a different slaughterhouse. The executive chef at Worthy Burger said he believed that the problem occurred at the previous slaughterhouse and not at the farm. To kill any harmful bacteria, USDA’s FSIS recommends that ground beef be cooked to a minimum internal temperature of 160 degrees F as measured with a food thermometer. The original story follows: The Vermont Department of Health is investigating a cluster of Shiga toxin-producing E. coli (STEC) infections in Vermont residents. As of Sept. 22, five laboratory-confirmed STEC infections and two probable cases have been identified. Two of the confirmed cases and one of the probable cases are children. No one has been hospitalized. Bradley Tompkins, epidemiologist with the Vermont Department of Health, told Food Safety News that all of those sickened had dined at Worthy Burger in South Royalton, VT. Valley News reported that Worthy Burger switched food vendors after being contacted by the health department and voluntarily closed for mechanical issues for several days and reopened Tuesday. The investigation into the food source is ongoing. Clinicians seeing patients who are experiencing symptoms consistent with an STEC infection are asked to immediately contact the health department’s Infectious Disease Epidemiology Unit and are encouraged to collect a stool specimen and have it tested for STEC. STEC infections can cause diarrhea (often bloody), nausea, stomach cramps and vomiting. Most patients recover from their illness. Approximately 5-10 percent of cases (especially children younger than age five) develop hemolytic uremic syndrome (HUS) as a result of their infection. (To sign up for a free subscription to Food Safety News, click here.)