As of Nov. 30, 2017, 636 cases of mumps had been confirmed in Hawaii, according to the state’s Department of Health (DOH).

The Hawaii DOH originally reported 14 confirmed mumps cases statewide in April 2017, but the number of confirmed cases has increased by more than 4,000% since that time .

The disease appears to be affecting both vaccinated and unvaccinated people, and has been confirmed in adults and children. In fact, approximately 60% of confirmed cases have been in adults 18 years or older. Complications caused by mumps infection have been reported, with 18 people experiencing orchitis – inflammation of the testicles – and hearing loss.

In the midst of the outbreak, the Hawaii DOH recommends that all adolescents between the aged 10-19 years old, and adults born in or after 1957, should receive an additional MMR vaccine dose as soon as possible. The outbreak dose is recommended regardless of previous vaccination or documented immunity to mumps. Administering additional doses of vaccine is not an ideal situation, the DOH noted, but said it should not cause any medical complications.

The Hawaii DOH will investigate mumps cases statewide as the outbreak continues.