Cleaning up vomit promptly is crucial to containing the spread of bugs like norovirus as 300 staff and students at a Jesuit high school in San Francisco discovered Wednesday.

The outbreak at Saint Ignatius College Preparatory school, initially believed to have been caused by a virus, sent a handful of the sickened students to hospital emergency rooms for treatment of dehydration, principal Patrick Ruff said.

School spokesman Paul Totah said roughly 300 pupils in all, out of the school’s 1,360-member student body, were believed to have been affected in some way.

Extra maintenance staff were brought in to scour the entire school with a bleach-based solution, and the process will be repeated on Thursday, Ruff said.

The school consulted with San Francisco health inspectors, who visited the school Wednesday and ruled out cafeteria food or waterborne sources for the outbreak, he said. Further testing is needed to determine whether norovirus, a common cause of gastroenteritis, was the culprit.

Dr. Tomas Aragon, San Francisco’s chief medical officer, said the outbreak may have originated from a single infected student who got sick in an often-used doorway.

"A student vomited on central doors, on the rods that open these big doors. Then the bell rang and a lot of students went through that door."

Aragon said the norovirus can survive on surfaces for days and is highly contagious.