Share prices were down more than 4 percent Tuesday after five people in Oklahoma, Kansas and North Dakota with E. coli reported having recently eaten at Chipotle.
Chipotle's woes began in late October after the first 19 cases of E. coli were linked to the restaurant chain. As of mid December, 53 people in nine states have had the illness.
Chipotle founder Steve Ells recently went on the "Today" show to assure customers the restaurant is enacting practices to prevent further outbreaks.
"Practices that are so far above industry norms today that this we will be the safest place to eat," Ells said.
But it wasn't enough to turn investments around. Since the outbreaks began, Chipotle's stock has slipped 18 percent to its lowest price in 19 months.
This video includes images from Getty Images.