Rosenthal is confident that the team of investigators has successfully identified the source of the disease.

"It's over," he said of the investigation.

But experts at CDC headquarters in Atlanta will attempt to tie up some loose ends.

UHS will draw blood samples from previously-afflicted students over the next few weeks. Antibody levels in the new samples will be compared to those in blood drawn early last month.

If testing can show that the epidemic spurred a rise in antibody levels, "that puts the case on firmer ground," Rosenthal said.

Officials have yet to determine the specific species of virus in the Norwalk family that caused the outbreak.

The CDC hopes to use further DNA sequencing to identify the particular strain. Rosenthal indicated last night that it might be a new species unique to Harvard.

Finally, CDC investigators are continuing to examine the link between the Harvard epidemic and a similar outbreak that occurred at Dartmouth College in late November.

The CDC is comparing stool specimens from Dartmouth with those at Harvard. That investigation will take between two and six weeks, Rosenthal said.

Dartmouth has refused to release a list of its food vendors to Harvard, according to Director of Dining Services Michael P. Berry.

Dartmouth spokesperson Alex Huppe said there was no further news on the source of the Dartmouth epidemic. Dr. Jack Turco who is leading that investigation, did not return several phone calls.

Inspection and Charges

Berry said that the recent epidemic has prompted a comprehensive investigation into the health standards of Harvard's food.

Already, Harvard has discontinued use with two vendors who supplied food in which bacteria levels were "unsatisfactory," Berry said.

Neither vendor was responsible for the food that may have caused the epidemic, Berry said, although both supply Harvard with produce. Berry declined to name the vendors.