Federal officials have declared that an outbreak of E. coli O157:H7 infections related to romaine lettuce on Wendy’s sandwiches has ended.

The Centers for Disease Control and Prevention is reporting that the total number of confirmed patients is 109, up from the 97 reported in its most recent update on Sept. 1. About half — 52 — of the patients have been so sick they had to be admitted to hospitals. Thirteen of the patients developed hemolytic uremic syndrome (HUS), a serious often life-threatening condition that can cause kidney failure. No one had died as of this evening.

As of the report tonight from the CDC the specific source of the E. coli could not be 100 percent confirmed. However, 83 percent of 82 patients for whom the information was available reported eating at Wendy’s before becoming ill.

“The true number of sick people in this outbreak is likely much higher than the number reported, and the outbreak may not have been limited to the states with known illnesses. This is because many people recover without medical care and are not tested for E. coli,” according to the CDC statement.

The CDC first announced the multi-state outbreak on Aug. 17 when there were 29 confirmed patients. On Aug. 19 the Wendy’s company removed lettuce from all sandwiches in a few states. The outbreak was initially limited to two states, but had grown to six states before being declared over. The states with confirmed patients are Indiana, Michigan, Ohio, Pennsylvania, New York and Kentucky.

The sick people reported eating a variety of menu items, including burgers and sandwiches. Samples of a variety of foods were tested, but the CDC did not say whether lettuce used for sandwiches was available for testing by the time the outbreak was identified.

Of 68 people with detailed information about what they ate at Wendy’s, 46, or 68 percent, specifically remembered eating romaine lettuce served on burgers and sandwiches.

“WGS (whole genome sequencing) showed that bacteria from sick people’s samples were closely related genetically. This suggests that people got sick from eating the same food,” the CDC reported.

Michigan and Ohio were the hardest hit with 70 and 25 patients respectively. Sick people ranged in age from 1 to 94 years, with a median age of 22 years; 55 percent were male. Their illnesses began on dates beginning July 26 and running through Aug. 17.

WGS analysis of bacteria from 108 people’s samples predicted antibacterial resistance to chloramphenicol, streptomycin, sulfisoxazole, tetracycline, and trimethoprim-sulfamethoxazole; analysis of bacteria from one person’s sample did not predict resistance to any antibiotics.

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