Officials at Horace Greeley High School in Chappaqua canceled afternoon classes Friday following an outbreak of a viral illness that left dozens of students and faculty sick.

On Thursday, 40 students came down with flu-like symptoms that included nausea and vomiting. Westchester County Health Department officials say in total more than 100 students and staffers have become ill. The outbreak was apparently caused by norovirus, which is spread from person to person through touch.

"This morning, we had a smaller number of students early on, and now some faculty and staff with similar symptoms, so we chose to close the school late this morning," says Chappaqua Schools Superintendent David Fleishman.

Some students are wondering why school officials did not cancel all classes.

"I think that the school should not have had school today at all because a lot of people went home yesterday," says 10th-grader Sam Pearlman.

The school building will be disinfected over the weekend. Officials hope the virus will be suppressed in time for Monday classes.

Health officials say antibiotics cannot be used to suppress the virus, which usually runs its course in 12 to 72 hours. They advise people to frequently wash their hands to prevent the further spread of the illness.