The mumps outbreak that started in Iowa has so far been confined to a handful of Midwestern states, but the virus's apparent ability to spread with the help of airline passengers means an outbreak could arrive in Hawai'i at any time.

Still, a state Health Department official said it's a marginal concern in the Islands, which sees a yearly average of 12 cases of mumps.

"We haven't seen the cases here and it's not as an alarming problem at the moment, and we don't suspect that it will be," said Kathie Fazekas, program manager/branch chief of the Department of Health's Immunization Branch.

Since the start of the year, Hawai'i has had three mumps cases, all originating outside the country. Fazekas said most of the mumps cases reported in Hawai'i are from Japan.

Close to 1,000 probable, confirmed and suspected cases have been reported in the Midwest outbreak, which started in December. Public health officials say it's the nation's worst mumps epidemic in 20 years. In recent years, the national average has hovered at 265 cases annually.

Mumps is largely spread by coughing and sneezing. There is no treatment, but serious complications are rare.

Symptoms are similar to the flu with one distinct difference: The salivary glands become swollen.

The United Kingdom has an ongoing mumps epidemic that has infected more than 56,000. It is believed the virus that set off the Midwest outbreak may have originated from the United Kingdom.

Fazekas said the fact that Hawai'i receives relatively few tourists from the United Kingdom is another reason not to be overly concerned about a mumps epidemic in the state. However, the Midwest outbreak is a potent reminder that preventable viral diseases such as mumps and measles are still a threat, she said.

Hawai'i children are required to get the MMR immunization — for mumps, measles and rubella — before entering school.

Fazekas said the state has a 98 percent childhood immunization rate.

Children should receive their first vaccination at 12 months to 15 months, and the second at 4 years to 6 years.

Fazekas pointed out the MMR vaccine does not use mercury as a preservative, a concern that may lead some parents to hesitate in following immunization guidelines.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.