Officials in Clark County, Washington — across the river from Portland, Oregon — have declared an emergency after identifying at least 71 cases of measles, most of which are in kids who aren't vaccinated.

The state has spent more than $1 million battling the outbreak, which began in January.

Before the US developed a measles vaccine, in 1963 , the contagious infection was a common childhood illness. Hundreds of children died every year, and millions more had symptoms.

As vaccination rates plummet in the US, officials are worried that outbreaks like the one near Portland will become increasingly common.

It's a public-health emergency and it's spreading fast: At least 71 kids and young adults have gotten sick with the measles in an area of Washington state just north of Portland, Oregon.

On January 22 the public-health department of Clark County, Washington, announced that at least 23 people were sick with the viral illness, which incubates for a week or two before prompting fevers, coughing, runny noses, and little red bumps that break out on the face and body.

Two days later the number of confirmed measles cases had risen to 25. A day later, the number rose to 30 confirmed cases. To date, at least 71 people have fallen sick with the measles in Clark County, in an outbreak that's now costing Washington more than $1 million.

The illness can be deadly.

Fifty-two of the sick people are age 10 or under, and so far the public-health department has confirmed that 62 of the 71 didn't get their measles vaccine. One person was hospitalized but has since recovered.

Even though the vast majority of cases are in unvaccinated kids, at least two people who had received a single dose of the measles vaccine got sick, too. It's a harsh reminder that the vaccine is not perfect. Still, a full course of two doses is about 97% effective at stopping the measles, while that single dose is 93% effective.

The sickness is spreading beyond county lines. One man in his 50s who said he'd been in Clark County took measles home with him to King County, Washington. He's since recovered, but county health experts are still worried.

"Measles is a highly contagious disease, and if you don't have immunity you can get it just by being in a room where a person with measles has been," Dr. Jeff Duchin, a health officer for Public Health in Seattle and King County, wrote in a blog post detailing locations where the man had been when he was infected.

The outbreak is not confined to Washington state. Across state lines, in Oregon, a resident of Multnomah County, the Portland metro area, has also contracted the measles, the Oregon Health Authority confirmed Wednesday. Two infected, unvaccinated kids recently traveled from Washington to Hawaii, but they were quickly quarantined and have since left the Big Island, The Oregonian reported. Two more of the people who contracted the measles in Clark County have since moved to Georgia, where vaccination rates are higher.

This is exactly the kind of scenario public-health experts have been warning about. In 2018, the World Health Organization said measles cases had surged by 30% around the globe, with some of the biggest hikes in places like the US and Europe, where more parents are opting not to give their kids recommended shots like MMR (protecting against measles, mumps, and rubella).

"This is something I've predicted for a while now," Peter Hotez, the dean of the National School of Tropical Medicine at Baylor College of Medicine, told The Washington Post. "It's really awful and really tragic and totally preventable."

A perfectly good and safe measles vaccine

An Iraqi doctor at a clinic in Baghdad preparing a vaccine injection to protect a girl from measles, diphtheria, tuberculosis, and hepatitis B. AP Photo/Manish Swarup

The measles vaccine was developed in the US in 1963. Before then, measles was a common childhood ailment that would kill 400 to 500 people every year in the US and sicken 3 million to 4 million others. As more kids got shots and oral doses of the vaccine in the decades after 1963, measles rates plummeted.

In 2000, the Centers for Disease Control and Prevention said measles was effectively eliminated in the US because the virus was not being transmitted year-round anymore and there were fewer than 100 cases a year. But increasingly kids in the US are now going without their shots.

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An abandoned measles ward on Ellis Island. Ellis Island Portfolio/New York Public Library Public Domain Collection

Outbreaks in the US have more become common where unvaccinated people cluster and parents sometimes forgo shots for religious or personal reasons. There was one in the Orthodox Jewish community in Brooklyn last year and in Amish communities in Ohio in 2014.

Other parents mistakenly believe that there's a link between autism and the measles vaccine. This is chiefly because of discredited research by the scientist Andrew Wakefield. His main paper on the subject has been retracted, and many other studies since then have found no link between autism and vaccines. But the spread of misinformation and anti-vaccine campaigns (like those that targeted a Somali-American community in Minnesota) have led to more frequent outbreaks.

A 2018 report on the state of the US "social movement" not to vaccinate children found that Portland was one of the more dangerous "hotspots" where people weren't vaccinating their kids despite doctor recommendations. (Other spots of concern included Seattle, Phoenix, Salt Lake City, Houston, and Detroit.)

"Without urgent efforts to increase vaccination coverage and identify populations with unacceptable levels of under- or unimmunized children, we risk losing decades of progress in protecting children and communities against this devastating, but entirely preventable disease," Soumya Swaminathan, a deputy director general at the WHO, said in a recent statement.

2014 and 2018 were both banner years for measles in the US, with 667 and 349 confirmed cases.

What a measles infection looks like

A child with measles. Centers for Disease Control and Prevention

There's really no way to prevent someone from getting the measles other than a vaccine. The virus can easily spread when an infected person coughs, sneezes, or breathes on others.

It takes one to two weeks after the infection for measles symptoms — which can include, fever, cough, runny nose, and watery eyes — to show up in a kid.

Often, parents notice white spots, called Koplik spots, appearing in an infected child's mouth about two to three days after the onset of symptoms. After a few more days, a rash breaks out, and flat red spots that may first appear on the face can cover the child from head to toe, developing into raised bumps.

With any luck, the rash and fever persist for only a few days before the child gets well again.

But deadly measles complications affect about one in every 1,000 people with measles. These can include pneumonia, encephalitis (brain swelling), and a rare disease called subacute sclerosing panencephalitis that doesn't show up until seven to 10 years after a person has had the measles.

Before 1963, about 4,000 Americans developed brain swelling from measles every year. The encephalitis, when it didn't kill them, sometimes left people deaf or with brain damage.

This story was originally published on January 23 and has been updated with the latest counts of measles cases.