Background

The state of Iowa has been experiencing a large outbreak of mumps that began in December 2005.  As of April 17, 2006, there have been over 1200 suspect, probable and confirmed cases of mumps reported in Iowa and surrounding states.  Additional outbreak-associated cases are being found in several other states throughout the country.

Arizona does not currently have an outbreak of mumps, but Arizona Department of Health Services, with the help of the local health departments, is following up on any reported cases of mumps and/or parotid gland swelling.  It is expected that one or more cases of mumps related to the Midwest outbreak will be identified in Arizona.

Mumps is usually a mild disease with the main symptom being parotid gland swelling, but an estimated 20-30 percent of mumps infections are asymptomatic.  Symptomatic mumps infections can have other clinical manifestations including aseptic meningitis, encephalitis, orchitis, hearing impairment, or miscarriage.

Mumps is transmitted via respiratory droplets. The incubation period for mumps is usually 16-18 days, though it ranges from 12-25 days.  The infectious period is considered to be 2 days before parotitis onset to 9 days after parotitis onset.

A history of mumps vaccination should not exclude the consideration of mumps in a patient with swelling of the parotid or other salivary glands that lasts >2 days.  Mumps vaccination is very effective, with 95-99% protection after just one dose.  In the current Iowa outbreak, however, most of the cases have been previously vaccinated.  To give optimal protection, 2 doses of MMR should be provided in schools and health care settings to minimize the risk of spread in those environments.

Due to the size of the Midwest mumps outbreak and the potential for spread to Arizona, the following guidance is provided to define mumps cases, guide surveillance, assist in diagnosis, give recommendations for excluding cases and unvaccinated children from school, and give immunization recommendations for children, teachers, health care workers, and the general public.