Centers for Disease Control and Prevention

A 3D graphic representation of a spherical-shaped mumps virus particle.

The Maricopa County Department of Public Health say Maricopa County is experiencing an outbreak of mumps at levels not seen in decades.

The department has confirmed 12 cases of mumps since August — that’s five times as many as it normally sees.

Medical director Dr. Rebecca Sunenshine says normally people diagnosed with the mumps have recently traveled internationally, but the new Maricopa County cases were all contracted locally.

“That tells us that there’s a lot more cases out there that haven’t been diagnosed and haven’t been reported to public health,” she said.

Sunenshine says Maricopa County has lost its community immunity due to declining vaccination rates, so diseases like mumps can now spread easier.

While none of the 12 patients died, one was hospitalized. Dr. Sunenshine says the department also is worried about measles and encouraged everyone to get the measles, mumps, rubella vaccine.