Public health milestones should be permanent, not temporary. But less than 20 years after health officials declared that measles had been eliminated in the U.S., the nation is on the verge of losing that vital status.

It’s a chilling development that simply should not be happening. Measles is a highly contagious and potentially deadly disease, causing 110,000 deaths worldwide in 2017. But it is also vaccine-preventable, with shots to guard against it widely available in developed countries.

As appalling as this death toll is, the number was once far higher. “Before the introduction of measles vaccine in 1963 and widespread vaccination, major epidemics occurred approximately every 2-3 years and measles caused an estimated 2.6 million deaths each year,” according to the World Health Organization.

That deadly history is why doctors at Mayo Clinic and elsewhere are sounding the alarm about the warning from the U.S. Centers for Disease Control and Prevention (CDC) this summer about the potential for the nation to lose its measles elimination status.

That designation, made in 2000, didn’t come all that long ago in historical terms. What it means is an “absence of continuous disease transmission for greater than 12 months.” The goal of achieving it was first announced in 1966 and again in 1978, when the CDC aimed to accomplish this by 1982. It took an additional 18 years — a reminder of how hard it to control ­measles once it gains a foothold.

In May, the CDC announced that the number of reported measles cases this year had surpassed a high-water mark set 25 year ago. The 2019 U.S. total now stands at 1,234. Illnesses have been reported in 31 states, though not Minnesota.

The CDC notes that the majority of cases occurred “among people who are not vaccinated against measles.” Medical providers and health officials in Minnesota and elsewhere must do more to counter the debunked myths being spread on vaccine safety, a key reason vaccination rates have dipped.

The Minnesota Legislature also needs to step up. Other states have closed loopholes that allow parents to cite religious or conscientious beliefs in opting out of immunizations otherwise required for school-aged children. The crumbling of the public health milestone on measles should spur lawmakers here to finally act.