The state Department of Health has initiated an investigation into an outbreak of norovirus, a highly contagious gastrointestinal disease, at a Kapolei nursing home.

The outbreak at Ka Punawai Ola has affected both patients and staff at the 120-bed facility, but DOH said it was not sure yet of how many people were infected.

"So far we haven't identified any deaths that were related to the virus," said DOH spokeswoman Janice Okubo, adding that the care home is taking precautions against further spread of the illness.

"They're sanitizing, cleaning surfaces, cleaning areas, isolating patients that are ill so that they don't expose other people," Okubo said.

Norovirus symptoms usually start with acute vomiting, watery non-bloody diarrhea with abdominal cramps, and nausea. There may be low-grade fever, and dehydration is the most common complication, especially for the young and elderly. Symptoms last about 24 to 72 hours.

"When elderly-care homes have issues with flu or norovirus it's really serious, because they're frail or fragile," Okubo said, adding that the disease is common in settings where people live in close quarters, such as care homes, cruise ships and hotels.

The facility kept out visitors for a short period, she said.

The DOH first learned about the problem when laboratory tests on patients came back positive for the virus, Okubo said. She said she wasn't sure how long the investigation will take and it's possible that they will never identify the original source of the infection.

"With norovirus, 30 percent of the people who may have norovirus may not exhibit any symptoms," she said. "So they may be spreading the illness but not know that they have it. We just want to make sure that any further illnesses are stopped."

Cullen Hayashida, a staffer at the Kupuna Education Center at Kapi'olani Community College, said the facility should follow standard precautions to bring the virus under control.

"It's a lengthy process to get rid of it and it's always in the background ready to crop up," said Hayashida, a long-term care coordinator. "You have to be extra careful to keep the place extra clean."