Hartford City health department officials are interviewing cafeteria workers at Aetna’s downtown Hartford office, where five employees have been stricken with E. coli in the last three to four weeks.  The source of the outbreak has yet to be determined, and the cafeteria remains open, company spokesman Fred Laberge said today.  The most recent case occurred about a week ago, when an employee went to the company’s wellness center complaining of feeling ill. He was taken to an emergency room and admitted to hospital but has since been released, Laberge said. The other employees did not require hospitalization.