Let me take a guess. I am not trained in the medial field at all BUT I would venture to say many were illegal or around illegals who have never been vaccinated!! I am more puzzled by the fact that they are puzzled.
The mumps vaccine contains live, but “weakened”, mumps virus. That is the source of the outbreak.
Liberals are puzzled by everything.
Liberals are puzzled that malaria increases dramatically when they outlaw DDT.
Liberals are puzzled that there are food shortages when price controls are placed on the cost of foods.
Liberals are puzzled when they kowtow to vicious dictators, who then run things like vicious dictators.
Liberals are puzzled when taxes go down, but revenues go up.
Liberals are puzzled when they bring in a Spotted Wart Fly to control the population of a Southern Striped Gnat, and the gnat doesn’t go away, but the Spotted Wart Fly population spirals out of control and becomes an environmental menace.
Liberals are puzzled when they make lavish deals to give dictators money and credibility in exchange for stopping some activity, but the activity continues as if there were no deal, and we keep giving money.
Liberals are puzzled when they create laws that force lenders to give loans to people who cannot possibly pay them back, and the lender goes out of business.
Liberals are puzzled when they guarantee payer loans with federal tax money, and lenders give money freely not with respect to the fiscal soundness, but with respect to how many loans they can underwrite in the shortest period of time, because they know they will get their money.
Liberals are puzzled when the government goes broke and the economy tanks because all the previously mentioned loans are never repaid by the borrower, and the taxpayer is on the hook.
Liberals are puzzled when they let a criminal with a lengthy or violent record out of jail early to give them a new start on life, and they break the law or murder someone within a few days of release.
Liberals are puzzled that terrorists prisoners released in various deals return to terrorism.
Liberals are puzzled when they create the largest, most byzantine, and most expensive health care government program in history called the Affordable Care Act, and it isn’t affordable.
Liberals are puzzled when they force women and open homosexuals onto combat ships, and sexual infractions go up, and morale and efficiency go down.
Liberals are puzzled when they do everything in their power to suppress the exploitation of native energy sources such as coal, oil, and nuclear, and prices go up with accompanying brownouts and blackouts.
Liberals are puzzled when they regulate the hell out of an industry, and that industry moves out of the country.
Liberals are puzzled when state and local pension programs are so lavish and unsustainable that the town must declare bankruptcy.
Liberals are puzzled when they advocate for government totalitarian control of people, and they are among the first dragged out of bed and lined up against a wall to be shot by their fellow tyrannical liberals.
Liberals are puzzled when they support Islamic beasts who vow to kill westerners/jews/homosexuals/capitalists/christians/women/homosexuals and then actually kill them.
LIBERALS ARE PUZZLED WHEN THEY WHIP THEIR WEAK-MINDED, SLAVERING, SPITTLE-LIPPED ACOLYTES INTO A HOMICIDAL FRENZY AGAINST THOSE THEY DISAGREE WITH, AND...THOSE WEAK-MINDED, SLAVERING, SPITTLE-LIPPED ACOLYTES ENGAGE IN HOMICIDE.
Thing is, liberals understanding of anything is a mile wide and a nano-meter deep. Scratch the surface with a sewing pin, and for them, they are in uncharted territory. So, I don’t doubt for one second that these things “puzzle” them.