Harvard and Cambridge officials scrambled yesterday to find clues to the identity of a vomiting epidemic that mysteriously struck hundreds of students Tuesday night.

University Health Services (UHS) director David S. Rosenthal '59 said yesterday that more than 150 students were admitted to the health service Tuesday night. A handful of undergraduates came to UHS with similar flu-like symptoms yesterday, but Harvard officials said that all but a small group of students were feeling better and had returned to their regular schedules.

In a clear sign of the seriousness of the problem, the Centers for Disease Control (CDC), a U.S. government run unit in Atlanta, confirmed late yesterday that one of its scientists would fly to Cambridge to investigate. The scientist will begin his probe tomorrow, according to a spokesperson for the state department of public health.

Doctors and nurses at the University Health Services had told students admitted there Tuesday night that they were likely suffering from food poisoning. But UHS director Rosenthal backed away from that assessment during a conference call with two other Harvard administrators and a Crimson reporter yesterday.

Instead, Rosenthal and other Harvard officials pointed to a similar at outbreak at Dartmouth last weekend as a possible explanation for the epidemic.

Starting Friday at 2 p.m. and continuing through Saturday, approximately 100 Dartmouth students began vomiting, and several were hospitalized, according to Alex Huppe, news director at the Hanover, N.H. school, Dartmouth officials have not been able to determine a cause of the outbreak, though a virus is believed to be the culprit.

Joe Wrinn, director of the Harvard news office, said University officials had studied recent athletic department schedules in an effort to determine any recent times when Dartmouth and Harvard students had met.

"[The epidemic] is very similar to what happened at Dartmouth," Rosenthal said. "The symptoms are strikingly similar, which points to the fact it may be a virus."

The epidemic made for a macabre scene in the lobby of the UHS urgent care entrance under Holyoke Center Tuesday night. Several students were slumped on couches with pink plastic basins placed next to them to catch their vomit. Others were collapsed on the floor, barely appearing to breathe.

The ill were mostly first-years but also included students from both the Quad and the river houses.

Harvard officials began interviews with the sick yesterday, and written surveys were also being sent to proctors for dissemination. Administrators said they would question unaffected undergraduates in an attempt to establish a "control group."

So far, interviews by both Harvard and The Crimson have turned up little evidence of food poisoning.

"There's no common food they ate," said a relieved if puzzled Berry, who said yesterday afternoon that he had already talked to a number of students himself. "We also haven't been able to find a common room they've all been in."

Berry said the dining services' strong safety record, including a perfect evaluation at its School of Public Health facility on Tuesday, made food poisoning seem less likely.

Asked if food poisoning was no longer being considered as a possible cause of the epidemic, Berry said it was too early to rule anything out.

As of late yesterday afternoon, 33 students remained at UHS, some of whom were receiving fluids intravenously. Acting President Albert Carnesale visited these undergraduates and also met with Rosenthal, Berry and other officials to discuss the situation, sources said.

Inspections

Early yesterday morning, inspection teams from the state and city joined investigators from the Harvard Dining Services, the University's facilities maintenance department and the Environmental Health and Safety office at the Union. In all, nearly two dozen people were investigating, Berry said.

In addition to water tests performed by the city, three dozen samples of leftover Union food from Tuesday as well as stool from dining service employees and sick students were being examined. Some students also received blood tests, Rosenthal said.

Test results are expected today and tomorrow.

Some samples were being tested at the UHS clinical laboratory, while others were sent to Morrell Associates in Marshfield, Mass. Morrell officials declined to comment last night.

But yesterday ended with more answers than questions about the cause of the epidemic. "At this point, we're stumped," said an official from Harvard's Environmental Health and Safety office, who spoke on condition of anonymity.

College health experts said they could recall few times when a college had been struck by such a large epidemic. The size of the epidemic, some said, argues for an explanation other than food poisoning.

"It's really unusual the way food is prepared in dining services to have food poisoning in that large a number of people," said Dr. Harris Faigel '56, director of the Brandeis health service for 19 years and treasurer of the New England College Health Association. "Usually, you have food prepared in a series of small batches, and you do not contaminate it all."

Rosenthal said he spoke yesterday with his predecessor as UHS director, Dr. Warren E.C. Wacker. Wacker was unable to recall a campus epidemic of such severity, Rosenthal said.

"When you have a large group of people eating together or living together, there is always the possibility that something like this can happen," said Sean Fitzpatrick, spokesperson for the state department of public health. "But it certainly is newsworthy when you have this amount of folks affected."

Ed Dowling, a chemist with the Cambridge water department, said preliminary tests yesterday strongly suggest the epidemic was not caused by anything in Harvard's water supply. Water department officials were unable to find any evidence of coliform bacteria or other common types of contamination, he said.

At the same time, Dowling cautioned that final results of water tests will not become available until this afternoon.

"We found no problems today," he said, "but just as a precaution we took a sample."

Dr. Melvin H. Chalfen, the commissioner of health and hospitals for Cambridge, supported Dowling's statements. He said there had been no suggestion of water contamination in any part of the city's supply, but cautioned that tests are not yet complete.

Progress yesterday came in the form of possibilities ruled out rather than new leads developed. Harvard, city and state officials, who worked together in a tandem that one source happily labeled "efficient," said they had been able to rule out some kinds of food poisoning. They also said the epidemic could not be attributed to any problem in a Chemistry 10 labs, as some students had suspected.

Harvard said it had contacted the Centers for Disease Control, but state officials indicated they had officially called for help with the investigation.

"CDC has been asked to assist in an investigation," CDC spokesperson Bob Howard said yesterday. "If a state wants aid or assistance, they ask and we become involved. We're sort of the 911 of the public health apparatus."

Howard promised that the CDC investigator will provide Harvard with aggressive "shoe leather epidemiology."

Chuck Krause, an official with the Environmental Health and Safety office, said ventilation systems in the Yard and the Union had been checked, but there was no evidence that anything in the air had caused the epidemic.

Workers at the Freshman Union--who spoke on condition of anonymity because they said they were instructed not to talk with reporters--said they were shocked by the news. All of the workers eat the same meals as students, and only one has so far turned up ill, according to the workers and Berry.

"I was totally shocked," said one dining hall workers. "We eat the same meals, but no one I know of is sick."

Missed Exams

An undetermined number of students missed an exam yesterday in Social Analysis 10, Harvard's largest class. Some section leaders in "Ec 10" began the exam period by offering any sick students the opportunity to delay their tests. Dean of Freshmen Elizabeth S. Nathans sent electronic mail explaining the epidemic to academic departments with problems sets and bests scheduled for yesterday and today.

"Clearly these students have been in no condition to complete work they anticipated doing on the evening of [December 6] and cannot reasonably or appropriately be expected to attend classes on [December 7]," the e-mail message said. "Those who remain in Stillman on IVs will probably be unable to complete work due [December 8] as well."

The Stillman Infirmary did not have enough beds for the crush of students. A dozen beds were set up in the UHS library and 10 were added in the solarium, according to Harvard spokesperson Joe Wrinn. In addition, three cots were set up in a storage area on the third, floor, Wrinn said.

A UHS source said last night that while the health service seemed to respond well to the epidemic, the overflow crowds and lack of beds highlighted problems. The source noted that financial considerations have forced Rosenthal to reduce the number of medical staff by attrition.

UHS doctors and nurses were discussing the epidemic as a case of food poisoning, the source said.

Confusion marked parts of yesterday's operations. While the University advertised two UHS "hot lines" for clinical and administrative information, health service employees answering the phone at those numbers had no information and no idea they were hot lines. "I'm afraid I'm not very hot," a staff member at one of the lines said.

Precautions

The Union closed for breakfast but re-opened for lunch and dinner, contrary to some reports on TV news. The kitchen was not used yesterday, and food served in the first-year dining hall was prepared at a separate facility at 80 JFK St.

To prevent contamination, meals at the Union were wrapped in cellophane and served in sanitized, plastic containers. Only canned drinks were available.

Traffic was light at the Union, however, as many first-years opted to dine at local restaurants or the house dining halls. "We've all been sick with colds so there is no way we will risk our stomachs as well," said Jocelyn M. Walker '98, who ate dinner at Chili's with five of her friends.

Elizabeth T. Bangs, Marios, V. Broustas, Joshua L. Kaufman, Joe Mathews and Rajath Shourie contributed to this report.