(CNN) Fainy Sukenik believes in vaccines, and her four children are up to date on all their shots.

That's why she's furious that her baby got measles. Too young to be vaccinated, 8-month-old Shira Goldschmidt developed complications from the virus and had to be hospitalized.

Infectious disease experts say the cause is clear: anti-vaxers.

Both in the United States and in Israel, where Sukenik lives, the ongoing measles outbreaks started with pockets of people who refuse to vaccinate their children. Those anti-vaxers can then spread measles to babies outside their communities because even if parents want to vaccinate their children, babies don't get their first measles shot until their first birthday.

"I'm so angry and so frustrated," Sukenik said. "On Facebook, I wrote to the anti-vaxers, 'you are hurting our kids because of your choice.' "

Infectious disease experts say this same scenario is bound to happen in the United States too and may have happened already: Anti-vaxers who've chosen not to vaccinate will spread measles to babies under age 1 whose parents want to vaccinate them but can't because they're too young.

"It's absolutely inevitable," said Dr. Peter Hotez, a vaccine scientist at the Baylor College of Medicine in Houston.

The virus is so contagious that a baby under the age of 1 could get it by entering a room where someone with measles had been two hours before, according to the US Centers for Disease Control and Prevention

"Our babies are no different than Israeli babies," said Dr. William Schaffner, an adviser on vaccines to the CDC. "And the measles virus in Israel is the same virus as here in the US."

Baby Shira's story

Shira Goldschmidt a week before she contracted measles.

Shira got sick in December with a runny nose and a 104-degree fever. Her parents took her to the doctor, who said that it was just a regular virus and that she would soon recover.

When the red spots appeared a few days later, her parents knew it was measles.

"It wasn't just dots on one part of her body. They were everywhere: inside her mouth, between her fingers, in between her toes," her mother said. "I'm an experienced mother, and never ever have I seen something like this. I was really scared."

By this time, Shira couldn't eat and could barely drink, her breathing was shallow, and she was so weak she couldn't even hold her head up.

Sukenik and her husband took Shira to the hospital, where she was put in isolation and received intravenous fluids.

In December, Sukenik wrote an emotional post on Facebook

"Let's talk for a moment about freedom of choice for those who believe that vaccinations are Satan and the source of all evil," Sukenik wrote in Hebrew. "It should be stated that they have a right to believe in anything they choose, but we should also talk about the price that others pay."

She suggested that anti-vaxers either "stay in enclosed areas or hold a big banner noting that you are anti-vaccine."

"Are you ashamed that you don't vaccinate? No, you're not ashamed. So you should wear a sign and let me choose whether my kids will play with your kids," Sukenik told CNN in an interview.

US outbreak started in Israel

The largest and longest of the ongoing measles outbreaks in the United States started last year when an unvaccinated ultra-Orthodox Jewish child in New York visited Israel and became infected.

Then, it spread further. Recently, an infected person traveled from New York to Michigan and spread measles to 41 people there

The outbreak in the United States isn't nearly as large as the one in Israel, where there have been almost 4,000 cases since March 2018. In about the same time period in the United States, there have been fewer than 1,000 cases.

"These measles outbreaks are remarkably persistent," Schaffner said.

The results can be devastating: For every 1,000 children who contract measles, one or two will die, according to the CDC

'I am not afraid'

Shira turned 1 this week.

"Now, baruch Hashem, Shira is OK; she is happy; she has started walking," her mother said, using the Hebrew phrase for thanking God.

But she isn't completely out of the woods. Doctors told her parents that she could still experience devastating complications of measles in the years to come.

It rarely happens, but about seven to 10 years after someone has measles, they can develop subacute sclerosing panencephalitis, a disabling and deadly brain disorder, according to the CDC

Among people who contracted measles during a resurgence in the United States in 1989 to 1991, 4 to 11 out of every 100,000 were estimated to be at risk for developing the disease.

"For years I'm not going to be able to rest from this fear," Sukenik said.

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Sukenik says her Facebook post has received more than 4,000 comments, both positive and negative. She said anti-vaxers have called her a bad mother or theorized that Shira had a genetic defect.

But Sukenik will not be deterred.

"If they want to pick a fight with me, I am not afraid," she said. "I've seen in my own home what it means for a baby to have measles, and the responsibility is on us to make sure this epidemic goes away and this doesn't happen to another baby."