In cooperation with the federal Centers for Disease Control (CDC), the Freshman Dean's Office (FDO) yesterday continued to survey victims of last week's mystery epidemic--this time concentrating their questioning on the salad bar.

The survey, a follow-up to a more general initial poll, was given Tuesday to only some of the students who experienced flu-like symptoms, nausea and vomiting.

The survey asked students if they ate any of the items available in dining hall salad bars or ate bagged lunches during the period from Sunday, December 4 to Tuesday, December 6.

A preliminary study of the epidemic's possible causes is expected to be released today.

The first survey only asked students to describe their symptoms, where they ate and to choose what they had eaten from a list of food--without focusing specifically on the items in the salad bar. It included only the general option "salad bar" among a list of all the food served by the dining hall during the critical three-day period.

A University statement said the follow-up survey was part of the CDC and Harvard investigation to "evaluate the association between exposure to potential causes of disease and actual illness."

The epidemic afflicted hundreds of students, most of whom were first-years.

Investigators from CDC wrote the survey and gave it to the FDO for dissemination. They have already picked up most of the completed surveys for analysis.