Dean of Freshman Elizabeth S. Nathans, who was hospitalized last Tuesday, is suffering from a viral infection and is not expected to return for two weeks, University officials said yesterday.

"It now appears the most likely cause was a virus--a very serious viral infection of some kind," said Assistant Dean of Freshman for Academic Affairs Elizabeth Doherty, who is acting Dean of Freshman during Nathans' leave.

Nathans remains at Brigham and Women's hospital, but University officials said her condition is improving.

"She won't be back too soon, but will make a full recovery," Dean of the College Harry R. Lewis '68 said in an interview yesterday.

"It may be a couple of weeks," Doherty said, "but if you know Dean Nathans, you know it may be sooner."

Nathans was taken to the hospital last week after complaining of flu-like symptoms.

According to witnesses, Nathans excused herself from a breakfast meeting last Tuesday because she complained of feeling ill.

"[Nathans] thought it was like the flu," said Kristina M. Song '92, a senior proctor in Canaday who was at the breakfast.

Nathans, an notoriously early riser, had gone to work at the Freshman Dean's office before the 8 a.m. breakfast meeting at the Faculty Club.

The Senior Freshman Proctors with whom Nathans met said she appeared healthy.

"Everything was normal, and that's why it took us by surprise," said Senior Proctor Cally L. Waite of Pennypacker.

Thirty minutes into the meeting, however, Nathans excused herself, and was driven to Brigham and Women's Hospital by her son.

Doctors at the Hospital were unable to diagnose Nathans until Friday, when they decided the cause was a virus.

"By Friday it was pretty clear [that the cause was viral]," said Doherty, who has been in contact with Nathans' physician. "There's nothing infectious," she added.

--Marios V. Broustas and Sarah J. Schaffer contributed to the reporting of this story.