Wahiawa General Hospital officials hope the worst is over after an illness spread at an alarming rate over the weekend and into Monday.
The hospital said the outbreak affected 26 patients and six staff, but it was primarily to the first floor of its long-term care unit.
"Sunday we had 15 new patients, who were exhibiting symptoms and we had four on Tuesday, four on Wednesday and one on Thursday," said Don Olden, CEO of Wahiawa General Hospital.
Workers scrambled to move patients into isolation and then started an intense process of disinfecting the whole wing.
Olden said the hospital has not found a common thread yet.
"We are worried about the flu, but we are actually more worried about the norovirus infection."
State Health Department Infectious Disease Specialist Dr. Sarah Park.
It was concerned because the long term facility is connected to the main hospital by hallways.
"We limit the staff movement, so the staff are not moving between the skilled nursing and the acute hospital," said Olden.
Officials suspect the problem is a norovirus, a gastrointestinal bug that is also called "the cruise ship virus."
It causes severe vomiting and diarrhea and can be airborne and foodborne.