Health officials caution that they have not seen any cases of the more serious bacterial meningitis, which can be fatal if not treated.

The increase in cases has been seen at emergency rooms on O'ahu for a couple of months, said state Department of Health communications director Janice Okubo.

On Kaua'i, the outbreak is more recent and has brought an estimated 50 to 60 children and a few adults to the Wilcox Memorial Hospital emergency room and family physicians in the past few days.

"We've seen half a dozen in the last week, and there have been probably 10 times that many at the emergency room," said Dr. Bob Wotring, head of pediatrics at Wilcox. Most are treated and sent home, but some — those with severe vomiting who are unable to keep fluids down—have been admitted to the hospital, he said.

Wotring said doctors recommend that parents bring children with symptoms in for checkups if they display the symptoms. While antibiotics will not help a viral infection, some doctors may place patients on antibiotics until they are sure the disease is not bacterial.

There are many different viruses that cause viral meningitis, a term that refers to the irritation of the lining of the brain. The main disease-causing virus in this outbreak appears to involve intestinal distress as well as head and neck discomfort.

Viral meningitis, which normally clears up by itself in 10 days or so, is not tracked by the state health department, so the agency has no clear idea how many cases there have been.

"We have heard that there are increased cases on O'ahu, but we haven't heard from the other Neighbor Islands," Okubo said.

She recommended that parents with sick children keep them home from school or summer activities, where they could infect others.