An 18-year-old who graduated last week from T.C. Williams High School died early yesterday after falling ill during a beach trip with classmates.

Kelley Swanson had complained of nausea and weakness Wednesday in Salvo, N.C., where about 40 graduates had rented beach houses and were staying with chaperons. She was taken to a hospital Wednesday night and died a few hours later.

Although the cause of death had not been determined yesterday, a spokeswoman for the Virginia Department of Health said Swanson had symptoms of meningitis. The department issued a statement recommending that people who had close contact with her recently take antibiotics as a precaution.

No other students have been reported ill. Swanson's twin sister, Katie, was also on the trip.

In Alexandria, a close-knit community of teenagers and their families was reeling after hearing of Swanson's death -- the third in her class in two years. Last year, Laura S. Lynam, 17, died in a car accident on her way to a crew event; the year before, Schuyler H. Jones, 16, died after he was beaten in Old Town Alexandria.

"This class has gone through more than anyone should have to in high school," said Mark R. Eaton, an Alexandria School Board member whose daughter was on the trip.

"My daughter said it looked like some kind of flu symptoms," said Eaton, adding that she might have shared a room with Swanson. "Parents are of course concerned, and people are consulting physicians."

Beach week, while not an organized school event, is a T.C. Williams tradition in which seniors rent beach houses together after graduation. The teenagers left Saturday, the day after the ceremony, for what was to be a week-long trip.

Instead, parents in Alexandria were awakened yesterday by calls to come pick up their children in North Carolina.

Carolyn Beckett, whose daughter Elizabeth Coppelman, 18, has been best friends with the Swanson twins since she was 2, described her daughter and her friends as "numb." "Katie's in shock," she said. "She's in the shock of losing not just her sister but her twin."

Beckett said some teenagers were tested yesterday at a North Carolina hospital for meningitis, strep throat and other illnesses. Jarie Ebert, a spokeswoman for Outer Banks Hospital in Nags Head, confirmed that Swanson had died and that "services were offered in relation to this case."

Beckett said Swanson's mother and brother drove to North Carolina on Wednesday night but did not arrive before she died. "She's a nurse, and when she heard the doctor's discussions driving down there, she knew what it meant," Beckett said of Swanson's mother.

She added that Swanson's mother had said she thought the cause might be "a very, very bad strain of strep throat."

Friends and relatives described Swanson as an avid varsity soccer player who helped students with disabilities play the sport. Many spoke of her and her twin in a single breath.

"They were very active girls," said Steve Barrett, their uncle, adding that they were in the honors society and had planned to attend Virginia Tech.

Photos in the recent school yearbook show two blue-eyed redheads, one with straight hair and one with curls, who participated in many of the same activities, such as the Key Club and the yearbook.

Beckett recalled Swanson's "raucous sense of humor" and said she was "a last-minuter" while her twin got things done ahead of time.

"Katie and Kelley, you never needed to ask; they were always ready to help and be cheerful," she said. "In this community, you will not find a family that has been more quietly generous."

Whitney Post, a graduate who did not go on the trip, said her class had become unusually close because of its losses.

"It really just connects you and just brings you together," she said. "We all share the same grief."

That doesn't make it any easier. "This is getting really rough," Post said.

Kelley Swanson, shown on prom night, had planned to attend Virginia Tech with twin Katie.