An outbreak of measles is rampaging across Europe, taking a huge toll. In the first six months of 2018, there were 41,000 recorded cases of the easily preventable viral infection.

That six-month period saw nearly double the highest number of cases in a year since 2010 - which was 23,927 in the entire 12 months of 2017 - and lost 37 lives to measles. And according to experts in the US, that's what America could be facing too if parents don't vaccinate their children.

"We have a very serious situation," pediatric doctor Alberto Villani of Bambino Gesù Pediatric Hospital and the president of the Italian Pediatric Society in Italy told NBC.

"People are dying from measles. This was unbelievable five or 10 years ago."

And, yes, unequivocally, the reason for the severity of the outbreak is the fall in vaccination rates. In order to prevent outbreaks, at least 95 percent of the population needs to be vaccinated with two doses of the measles, mumps and rubella (MMR) vaccine.

In some parts of Europe, according to the World Health Organization (WHO), vaccination coverage is at less than 70 percent.

"It's the main factor leading to the outbreaks," Anca Paduraru of the European Commission in Brussels told NBC. "It's unacceptable to have in the 21st century diseases that should have been and could have been eradicated."

Measles is already on the rise in the US. Last year saw Minnesota's worst outbreak in decades, and earlier this year there was an outbreak in New York City. There's an outbreak underway in Brooklyn right now, with six cases cropping up last week, all of them in unvaccinated children (one too young to have been vaccinated).

Last year, the US Center for Disease Control studied the growing number of measles outbreaks in the US, and found that 70 percent of new cases occur in unvaccinated patients.

As we reported then, the anti-vaccination movement has been growing in recent years, partially thanks to a dishonest (and since retracted) 1998 study by former physician Andrew Wakefield, who was struck off the UK medical register for misconduct.

Wakefield's study used deliberately falsified results to make the fraudulent claim that there was a link between the MMR vaccine and autism - possibly to eliminate a rival for the alternative measles vaccine he had patented.

Although subsequent research has found that there is absolutely no link between vaccines and autism, never mind a causal one, many still believe it and refuse to vaccinate their children - including the MMR vaccine.

Measles has been eliminated from the US - that is, no new cases originate within the country - but outbreaks occur when it is imported from outside. The NYC outbreak was caused by a tourist, and the current Brooklyn outbreak was the result of an unvaccinated child travelling to an area in Israel currently undergoing a measles outbreak of its own.

"What has been happening in Europe is now happening in the US - on a smaller scale at this point," said Peter Hotez, director of the Texas Children's Hospital Center for Vaccine Development at Baylor College of Medicine.

But it could get a lot worse if something isn't done. A 2014 paper found that the efforts to correct misinformation were woefully inadequate compared to the concerted effort put in by anti-vaccination campaigners, who use the internet to spread their anti-science message.

That message is a lot more dangerous than you might think at first: if just five percent of a community refuses to vaccinate, this can have a disproportionate effect on public health, tripling the annual measles rate.

This, in turn, doesn't affect only the patients, but has an impact on the entire community - increasing hospital load and costing a conservative estimate of US$2.1 million for the public health sector.

Measles is also insanely infectious - and potentially deadly, particularly for small children. In 2016, there were 89,780 measles deaths globally, most of them in children under the age of 5.

And in the decade prior to the introduction of the MMR vaccine in 1963, there were between 300 and 700 deaths reported annually in the US due to measles.

"People don't see them and so they forget about them or they think the diseases don't exist anymore," said professor of medicine Jeffrey D. Klausner of the University of California, Davis.

"They don't realise their child is at risk for measles meningitis, encephalitis and permanent brain damage."