In recent months, Chipotle has lost customers, sales and profits after outbreaks of foodborne illnesses that sickened more than 500 people from Seattle to Boston. The burrito chain will shut its 1,900 U.S. restaurants on Monday for a meeting with employees to review a rapid overhaul of practices that it hopes will eliminate outbreaks of E. coli, Salmonella and norovirus. Food safety investigations in the United States begin – and often end – at the local level, and some states limit the disclosure of implicated restaurants, keeping diners in the dark.