pThe FDA said at least 22 people have been hospitalized and 13 states have been affected so far. Two people developed hemolytic uremic syndrome, which can cause acute kidney failure.
Of the 42 patients interviewed, all said they had eaten at McDonald's, and 39 said they had eaten a hamburger.
The Food and Drug Administration said in a statement that it is “using all available tools to confirm whether onions are the source of the outbreak.”
The agency said the investigation is ongoing, but Taylor Farms, a supplier of onion slices to the affected McDonald's restaurants, has begun a voluntary recall. He added that this supplier also has other customers who have been notified.
No cases have been reported to the Food and Drug Administration outside the United States.
Earlier this week, authorities initially reported 49 patients.
A specific burger called the “Quarter Pounder” in the United States is the focus of attention from the authorities.
McDonald's announced Tuesday that it would remove sliced onions from restaurants in the affected areas, as well as Quarter Pounders “as a precaution.”
Their lawyer, Ron Simon, told AFP that at least two complaints had already been filed on behalf of people who had contracted the disease. He is demanding a minimum of $50,000 each.
“The E. coli outbreak at McDonald's will be one of the largest food poisoning cases this year,” said Ron Simon, who represents 25 people in total. “Through this and other legal actions, we will ensure that all victims receive appropriate compensation,” he added.
E. coli bacteria cause stomach cramps, diarrhea and vomiting, which usually last three to four days. Most people recover without treatment, but some may develop complications.
Read also: Escherichia coli bacteria discovered in a McDonald's restaurant in the United States of America. What you should know about bacteria