This past Christmas holiday, an as-yet-unidentified “index case” — the first person to start an epidemic — visited Disneyland in California. Five employees became infected, along with dozens of visitors to the park. Since then, the outbreak has spread to about 80 people, including people who’ve caught it not directly from visiting Disney, but by coming in contact with Disney cases. These “secondary” cases will soon lead to “tertiary” cases — people who catch it from people who caught it from people who were at Disney. And on and on.

Such is the nature of epidemics, especially with a super-contagious illness like measles. We’re not talking Ebola, here — that can only spread from direct contact, touching the body fluids of someone who is dying from Ebola. No, measles spreads much more easily. Measles becomes contagious before symptoms start, and the infection can spread from the very air that someone who’s carrying measles breathes.

Fortunately, there is a very effective vaccine. With two doses, as recommended, there’s about 99 percent protection. That is a very effective vaccine. But in country with about 300 million people, even if 100 percent of us were vaccinated there would be 1 percent — 3 million — unprotected people. Add to that babies younger than one year, who can’t be routinely vaccinated, and people with immune deficiencies and other health problems that leave them vulnerable. Even if everyone who could get vaccinated got vaccinated, there would still be some vulnerable people. But we know that if just about everyone does get vaccinated, those vulnerable people are protected by “herd immunity” — with very little circulating measles, everyone is protected.

But what happens when people decide not to vaccinate? And what if a lot of those people live in the same neighborhoods and counties? We knew what would happen. It’s been an entirely predictable and avoidable catastrophe: a measles outbreak.

In the latest news, USA Today has been focusing on the spread of the epidemic, which has now extended outside of California into 4 more western states and Mexico. They also report that several California schools have sent dozens of unvaccinated children home to contain the spread of measles, including 24 students from Huntington Beach High School. CBS News has pointed out just how contagious measles is, and why this could end up being the beginning of a really huge outbreak.

Many reporters are drawing attention to the role of unvaccinated children in the spread of this epidemic. Almost all of the cases reported have been in unvaccinated children, including some babies too young to be vaccinated and many children whose parents chose to not get them vaccinated. A Washington Post blogger has illustrated the resurgence of measles from non-vaccination, all in one chart. At least one mom is mad that her child was singled out to stay home because she hadn’t been vaccinated for medical reasons — though, in fact, having a brother who had a severe reaction to a vaccine is not a contraindication to vaccinating a sibling. There is no “family tendency” that changes the estimated 1 in a million risk of a serious vaccine reaction.

The national media hasn’t focused on this much, but the State of California has declared that theme parks, airports, and other public places are not safe for people vulnerable to measles. That includes anyone who hasn’t been immunized — not just kids of non-vaccinating parents, but babies and people with immune problems. That’s right — the State of California now officially recommends that babies not go to airports. It’s not safe. Want to take your 9 month old to visit Grandma in Atlanta? You’d better drive. And don’t think about taking your baby to Disney in California — Disney says their parks are perfectly safe for  vaccinated people, implying that babies and others who are unvaccinated should stay away.

The international community has jumped on board, too. From Canada, a report points out the double-digit vaccine exemption rates in some California school districts, quoting a public health official, “When our immunity falls, it creates a problem for the whole community.” They also reached out for a quote from longtime anti-vaccine activist Barbara Loe Fisher, of the misleadingly named “National Vaccine Information Center.” (In all honestly, the “National Antivaccine Lies and Propaganda Center” would be a more fitting name.) Fisher illustrates her difficulties with understanding fractions by pointing out that a small number of people who’ve caught measles were vaccinated. Yes, but in an area where 90 percent+ overall are vaccinated, that almost all of the cases were unvaccinated tells you something about disease transmission.

Overseas, the BBC drew attention to one specific Orange County pediatrician, Dr. Bob Sears. Right in the heart of Orange County, home of Disneyland, Dr. Bob has been a longstanding supporter of non-vaccination — about half of his patients are unvaccinated. In some Orange County schools, 60 percent of children have a “personal belief exemption” so they can attend school without vaccines. The article quotes a professor who compares vaccine-denying parents to a drunk driver “who makes a socially irresponsible decision that can endanger not only his life, but also the lives of the other drivers and passengers on the road.”

Dr. Bob has responded to his critics, first in an odd, rambling Facebook post that tried to show that measles was nothing to worry about (though he admitted it could be serious for babies and immunocompromised people — but, apparently, we don’t need to be concerned about them.) He then petulantly responded to critics by calling them “stupid.” Classy, Dr. Bob.

I’m heartened to see that many media outlets have really come down hard on the so-called “anti-vaccine movement,” with headlines like, “Measles is horrible and is yet another thing the anti-vaccine movement is wrong about”. Yet some outlets are still posing this as a rhetorical question, like Yahoo’s “Is the anti-vaccination movement to blame for Disneyland’s measles outbreak?” Yes, Yahoo, it is.

As often happens, some of the best, in depth material about the outbreak has been coming from bloggers. Over at Science Based Medicine, Dr. David Gorski has covered the outbreak in detail (don’t miss the comments — a lot of great insights there too). He also illustrates the contributions of nincompoop anti-vaccine doctors like Dr. Jay Gordon, also of (you guessed it) California. Other superb blogs about the issue have appeared at the similarly-minded Respectful Insolence. Chad Hayes, MD, at his eponymous blog, approached this from a different angle in his piece “Dear anti-vax parents: We’re not mad at you.” Dr. Hayes is right — and that sometimes gets lost in the media swirl. It’s not the parents we’re mad at. It’s the people spreading lies, fear, and misinformation. Parents are caught in the middle, unsure who to trust, filled with worry. That’s a shame. Parents have been tricked into worrying about the vaccines, when it’s the diseases that cause the problems.

A lot of anti-vaccine (mis)information continues to appear. At least one Arizona doctor (an “integrative cardiologist,” whatever that is) proudly and clearly says “Don’t vaccinate your kids” — at least he’s not being a weasel about this. Let it all hang out, doc! And many mainstream reporters still seek out the usual few anti-vaccine docs for quotes in otherwise fact-filled articles, like this one from USA Today. There, Dr. Jay tells us that while there’s “no proof the vaccine is dangerous … It’s not a crucial shot.” In a New York Times piece, that same doc incoherently says: “I think whatever risk there is — and I can’t prove a risk — is, I think, caused by the timing. It’s given at a time when kids are more susceptible to environmental impact. Don’t get me wrong; I have no proof that this vaccine causes harm. I just have anecdotal reports from parents who are convinced that their children were harmed by the vaccine.” I think now is the time for reporters to stop going out of their way to quote these dangerous idiots.

I’ve saved the best for last — the parody sites, who’ve found this outbreak a rich source of terrific articles. What makes them so effective is that they all rely on that germ of truth. From the Onion, “Diphtheria excited about possibility of new outbreak”, and “I don’t vaccinate my child because it’s my right to decide what eliminated diseases come roaring back.” They’ve also got some great “quotes”, here and here, including the deliciously ironic “To be fair to the parents, no one could have predicted that neglecting to immunize people against diseases would lead to more people getting diseases.” Over at the Washington Post, an article that may have been written by A. Measles Virus is titled “Please stop vaccinating your children. I want to go to Disneyland.”

In all seriousness, this is just the beginning of an outbreak that could really be a catastrophe. Hundreds of thousands of public health dollars are being spent — and soon it will be millions. Parents and babies and children are missing weeks of school and work. Dozens of people are sick, and about a quarter of measles cases so far have had to be hospitalized. This really isn’t a joke at all. Hopefully, though, it will be a turning point. For those of you who still support and encourage parents not to vaccinate, now is the time to rethink your message. It’s time to end the “controversy” that never really existed. Vaccines are safe and effective, and we need to work together to protect all of us, including the most vulnerable.

Addendum: The measles outbreak has continued to spread, with 121 cases confirmed in 17 states as of February 9, 2015.

Roy Benaroch is a pediatrician who blogs at The Pediatric Insider. He is also the author of A Guide to Getting the Best Health Care for Your Child and the creator of The Great Courses’ Medical School for Everyone: Grand Rounds Cases.