McDonaldβs E Coli Outbreak Declared Over NYT > Science By: Teddy Rosenbluth 3 December 2024 at 17:54 Federal health agencies closed their investigations into the bacterial outbreak that sickened 104 people and was linked to onions on the fast-food chainβs signature Quarter Pounders. Β© Charles Rex Arbogast/Associated PressMcDonaldβs has not served slivered onions on its Quarter Pounder in several states since October, when the E. coli outbreak was first reported.