Illnesses linked to slivered onions on McDonald's Quarter Pounder burgers expand to 14 states, federal officials say.

Officials have confirmed that more than 100 people were infected by a severe E. Coli outbreak linked to slivered onions on McDonald’s Quarter Pounders, Forbes reported. The infections sent 34 people to the hospital and left four with a potentially life-threatening kidney condition called hemolytic uremic syndrome.

The source of the outbreak was likely slivered onions on McDonald's Quarter Pounder burgers, health officials have said.