Antananarivo, Madagascar (CNN) Measles found Hasina Raharimandimby and her family. Over three heartbreaking days in late January, three of her young children died of the virus.

"I miss taking them sweets and snacks for them whenever I came back home from work," she says. "We used to play and feed the birds near our home."

Madagascar, the island nation off the coast of East Africa, has been hammered by its worst measles outbreak in decades. The secretary general of the ministry of health told CNN that more than 50,000 people have caught the disease since October 2018 and there have been more than 300 deaths -- mostly children.

Madagascar, the island nation off the coast of East Africa, has been hammered by its worst measles epidemic in decades.

Hasina has brought her youngest surviving child to this clinic on a hillside in the center of Antananarivo because he has a cough.

After his siblings died, he was vaccinated during one of the four planned rounds of a massive campaign orchestrated by the government, UNICEF and the World Health Organization.

The doctor tells her the cough is nothing to worry about. It's just a common cold.

Because of its relative rarity in the developed world, measles is sometimes incorrectly regarded as a mild virus with limited impact. But it can take hold rapidly and cause encephalitis, deafness and in extreme cases, death, especially when a patient is malnourished or has a weakened immune system.

Hasina's children were only sick for a few days before they rapidly worsened and died. She says they weren't able to access the measles vaccines at the clinic when they wanted them.

"This is hard and I am bitter," she says. "You cannot always prevent death, but mothers should do all they can to protect their children."

An entirely preventable tragedy

When Lon Kightlinger retired from his job as state epidemiologist in South Dakota, he didn't think his past life would catch up to him quite like this.

"We heard rumblings of a measles outbreak in the capital between December and January and I just knew we were going to get hit," he says, inside a tiny clinic in Madagascar that's about three bone-jarring hours' drive from the capital.

Kightlinger worked in public health here as a young man. Now, well into his 60s, he has come back as a Peace Corp volunteer.

"Most of the other volunteers are young, idealistic and full of energy," he smiles, "but I bring a bit of perspective, I think."

That perspective helped him recognize the warning signs of a larger outbreak. "Our one doctor here, who has been practicing physician for 12 years, had never seen a case of measles until a month ago. And then boom, boom, boom, they started walking through the door. And it hasn't stopped," he says.

Three of Hasina Raharimandimby's children died of the measles. "You cannot always prevent death," she says, "but mothers should do all they can to protect their children."

In South Dakota, Kightlinger dealt with a measles outbreak, he says, but health workers managed to confine it to one extended family.

In Madagascar, the outbreak has hit every region of the country and all major towns and cities.

The measles virus is highly contagious -- it spreads through coughing and sneezing and can live in the air where an infected person coughed or sneezed for up to two hours. If someone who is not immune to the virus breathes the air or touches an infected surface, they can become infected. Its symptoms include high fever, cough, runny nose and pink eye, along with a red, blotchy rash all over the body.

Now, as several areas in the United States grapple with measles outbreaks, largely because of non-medical exemptions for vaccinations, Kightlinger and other experts point to Madagascar as a dangerous portent.

Throughout the country, private tragedies are playing out because of a lack of vaccine coverage.

Health officials here believe that vaccine coverage was at less than 50% at the start of this outbreak because of a weak, underfunded health system, and a failure of routine immunization delivery.

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For herd immunity to work -- when enough people are vaccinated that the disease can't get a toe-hold -- coverage needs to be at around 95%.

And for many Malagasy, it isn't through lack of trying.

"We Americans, we have concocted all of these excuses and reasons to be complacent about measles. The people in Madagascar they have busy lives as well. But when they do have vaccine drives, most of them will come out, travel long distances, and sit in the hot sun for their turn," says Kightlinger, who rides a bicycle several miles each week to deliver vaccines to nearby villages.

A stubborn threat

Ironically, some of the complacency in the developed world, is because of the very success of the public health response.

The first effective measles vaccine was developed in the early 1960s. Before that, there were an estimated 2.6 million deaths a year from the virus, according to the World Health Organization. In 2017, about 110,000 people died from measles, mostly children younger than 5, the WHO said.

But lack of understanding about measles and the rise of anti-vaccination beliefs based on phony science and social-media fueled conspiracy theories has a put a chink in the armor of otherwise well-protected countries such as the United States and France.

In a country like Madagascar, where they are still battling a deadly outbreak, that infuriates physicians.

"It is a question of mentality, because we need to convince those people. Maybe they don't know the reason why we should be vaccinated. Not only people in poor countries are not well educated," says Dr. Andosoa Rakotoarimanana, the director of the Ambohimiandra Children's Hospital in Madagascar's capital.

As the vaccination drive continues, he hopes that the vaccination coverage will get to much higher levels. But routine immunization is still the gold standard and there are still pockets of outbreaks.

This fight isn't over yet.

Jean Claude Nambinintsoa traveled for 24 hours in a mini-bus taxi to get his 15-month-old, Pierrot, to the hospital.

Jean Claude Nambinintsoa traveled for 24 hours in a mini-bus taxi to get his 15-month-old, Pierrot, to the hospital.

"I was hoping to get him vaccinated," he says as Pierrot clings to his neck, gently caressing his ear, "but when I got here they said that my son already had measles." He says that many children in his village got sick.

Pierrot is dangerously malnourished, his arms lost in the sleeve of his dusty striped shirt. Almost another casualty for a disease that humanity could defeat, but just can't seem to manage.

"It should be a wake-up call for not only for every person, for every health center in Madagascar, but for the whole world. These diseases come back and they clobber us if we are not protected," Kightlinger said. "These are living viruses who are very clever, and they will find us."