It was another brutal week for Chipotle Mexican Grill (NYSE:CMG) shareholders. The stock shed 8.5% of its value on the week, falling to its first weekly close below $500 in more than 23 months. 

We've now seen Chipotle close lower in nine of the past 11 weeks, and the cruel truth is that its latest 8.5% drop isn't even the biggest blow in the books during this pocket-draining run. The stock plunged 10% for one week in October, and it also suffered a 9.6% hit in November. Last week's drop was its biggest decline in December, but that's about it.

A new E. coli outbreak sent analysts scrambling to gnaw away at their stances, and there were plenty of bad gems breaking during the week to scare away potential bulls.

  • The Centers for Disease Control revealed on Monday that five people became ill with a new strain of E. coli, and all of them ate at Chipotle restaurants in Kansas or Oklahoma in November. 
  • JPMorgan Chase followed with a downgrade of the stock on Tuesday morning, fearing the comps will remain negative through at least the next four quarters.
  • Wells Fargo lowered its near-term profit forecasts on Wednesday. It also lowered its valuation range on the stock from between $505 and $520 to $480 and $505.  
  • Telsey Advisory Group slashed its price target from $575 to $555 on Thursday.
  • Market researcher Bespoke Market Intelligence put out a note on Thursday, estimating that just 9.5% of consumers visited a Chipotle in December. That's down from 14.1% in November. 

Chipotle investors may as well consider themselves lucky that the market was closed on Friday, given the way they were pelted with negative news on a daily basis last week. The few silver linings in the weekly carnage -- Chipotle's receiving clearance to open the Boston eatery responsible for the norovirus outbreak and the company's moving to improve the way it prepares its food for safety's sake -- were no match for the negative developments. One can also argue that Chipotle's changing the way it prepares its food can hurt more than help. Blanching onions, marinating raw chicken in resealable plastic bags instead of bowls, and possibly moving away from local sourcing may hurt either flavor or cost controls. If that wasn't the case, one would wonder why Chipotle wasn't doing it all along. This is no longer food with integrity. This is food with asterisks. 

We know that this isn't going to be a problem that reverses itself after what should be a dreadful holiday quarter. Wall Street pros have been slashing away at their forward profit targets, something that wouldn't be happening if the analysts thought Chipotle would be able to get back to where it was before its reputation took a hit anytime soon. This is going to sting, and it's going to linger. However, since no one seems to be thinking this is an outright Chipotle killer, this opens up the discussion for when the stock will start to bounce back -- especially if it's the pessimism that is now overdone. After seeing the stock fall in all but two of the past 11 weeks, it wouldn't be a surprise to see shares start to claw their way back before the fundamentals warrant a turnaround.