(NewsNation) — Dr. Donald Schaffner, a food safety expert at Rutgers University, says it’s not unusual for an E. coli outbreak to come from uncooked produce like the onions on the Quarter Pounder. He also says McDonald’s is taking the outbreak very seriously. Joining him on “Elizabeth Vargas Reports” was Teresa Murray, a consumer watchdog with the U.S. Public Interest Research Group. She’s concerned that the Centers for Disease Control and Prevention apparently informed McDonald’s about the onions last week but didn’t make the news public until this week.