Since August, public health officials in Maricopa County have confirmed at least 12 cases of mumps — five times more cases than they identify in a typical year.
The mumps virus, which causes swelling in the salivary glands, jaw pain, and general malaise, is usually spread through international travel. In the cases reported in Arizona, though, none of the patients had left the country. As the state sees declining vaccination rates, public health officials expect the disease to spread faster.
“We have been identified as a hotspot for a vaccine-preventable disease outbreak,” Dr. Rebecca Sunenshine, director of Disease Control for Maricopa County said.
In 2019, immunization coverage rates in Arizona schools have dropped below 95% for most vaccines, according to data from the Arizona Department of Health Services. Ninety-five percent immunization coverage is considered the standard necessary to prevent the spread of communicable diseases, according to the data.
“We’ve lost our defense from herd immunity, or community immunity,” Sunenshine said. “And that’s when enough people in the community have been vaccinated so disease can’t spread efficiently.”
Religious and personal exemptions for vaccines statewide have increased. Nearly 6% of sixth-graders are exempted from at least one major immunization. The Arizona Department of Health Services requires schools to report immunization rates for preschool, kindergarten, and sixth grade students.
At the county level, Yavapai County reports some of the lowest levels of immunizations: in 2019, only 83.3% of sixth-graders had the Measles, Mumps and Rubella (MMR) vaccination — nearly 10% below the statewide average. One-fifth of all students had personal belief exemptions for one or more vaccines.
Mumps is more prevalent in Europe and other places that Americans frequently travel to, according to Sunenshine. Mumps had been considered nearly eradicated in the United States, with fewer than 300 cases reported in the year 2000. So far in 2019, the Centers for Disease Control has reported more than 3,200 cases.
“We typically see cases of mumps that we know were exposed outside the country, but for these cases they haven’t had any international travel, so we know it’s spreading locally throughout the community,” Sunenshine said. “Both kids and adults all over the county have been affected, and we do suspect there are lots of cases out there that haven’t been diagnosed.”
Most people recover from mumps within two weeks, but the virus can cause serious complications and lead to hospitalization.
“There can be complications like pain or swelling in the testicles, or belly pain in females,” Sunenshine said. “Rarely we can see worse complications like inflammation around the brain and spinal cord, or encephalitis, and sometimes even deafness.”