CHAPEL HILL, N.C. — One part of the mystery illness at the University of North Carolina at Chapel Hill is solved.

Health officials said Thursday that the norovirus made hundreds of students sick.

Most people know it as the stomach flu. The kind of outbreak that hit UNC the past week has made headlines before.

The norovirus is kin to the "Norwalk virus" that has plagued the cruise-ship industry in recent years.

There also was the time 11 Duke football players got sick while on a trip to Florida State University in 2000. Doctors traced the virus to a boxed lunch.

The Duke case made history after the Duke players passed the virus to FSU players. It marked the first known time the virus had spread during a sporting event.

Noroviruses spread quickly. So officials at UNC are spreading the message for people to wash their hands. The virus can move from person to person, through food or water or from contaminated surfaces.

Health officials said Chapel Hill had an outbreak. There were 100 confirmed student cases. Two-hundred more students reported similar symptoms -- all in a week's time.

The source still was unknown Thursday.

UNC's student-health center kept good records of the student cases. But health officials said it is hard to know how far the illness may have extended beyond the campus.

Hank Lauver, who was recovering from the illness Thursday, is not a UNC student. But he said the virus traveled to his Garner living room.

"It was bad," Lauver said. "It really was."

A little detective work led Lauver to a recent lunch with a friend who became sick last week.

"We had lunch on Tuesday," Lauver said. "The salsa. But we've got a rule -- only a single dip."

Lauver's friend has a son who was sick first. The son goes to UNC -- giving Lauver his connection.

"That's how I kind of connected the dots," he said. "I'm confident that's how I got it."

Health officials said they have a harder time tracking cases like Lauver's because flu-like symptoms are common with lots of bugs. But they hope to connect more dots to find the exact source of the outbreak -- as well as prevent a future outbreak.

An interesting side note to this story: UNC recently conducted a study of the norovirus family. It found that 29 percent of people have a natural resistance to the viruses.