Piper Jaffray analyst Nicole Miller Regan says her review of the other foodborne illness outbreaks over the past decade suggests Chipotle Mexican Grill's comps are likely to experience at least some impact from the E. Coli incidents. Prior to the initial E. Coli news her channel checks suggested Chipotle's same-store-sales in October were running within her Q4 estimate of up 2.5%. "It is difficult to defend the unknown in terms of assessing, identifying and estimating the impact from the current situation," Regan admits in a research note. She nonetheless reiterates an Overweight rating on the stock with a $737 price target. The stock sold off $76.52 to $534.99 on Friday.