No cough, no measles. that was one of the many mantras and memory aids I learned in medical school. Most were designed to reduce tomes like Gray’s Anatomy to a few rules. Much of the time, it was easy to miss the point, especially when the subject seemed to be an obscure disease.

Five years into a typical Western medical education, none of us had ever seen measles. Nor were we bothered. Apart from HIV, microbes like measles seemed prehistoric. Still, I remembered this particular rule, offered by a revered professor, even as I wondered why he was so focused on a cough instead of “Koplik spots,” the little white dots in the mouth that are specific to measles.

Then I spent ten weeks in a pediatric infectious-disease ward in Cape Town. I thought I would see “African diseases” like hemorrhagic fever and HIV, which I did. But I also saw measles, rubella, scarlet fever, syphilis, rheumatic fever, typhoid, tuberculosis and many other causes of rash and fever. Suddenly, I could see the point of my professor’s rule. The very first signs of measles are a fever and cough, followed by a runny nose and red eyes. The appearance of a rash three or four days later is usually what prompts parents to bring their child to the emergency room. The problem is that, at any given time, half the preschool children in the ER have a fever, rash or both. The differential diagnosis—which can range from mild roseola to devastating meningococcal sepsis—is hard enough in immunized children. In an unimmunized child, the ailment might also be rubella—harmless for the child, but catastrophic for unimmunized pregnant patients—or chicken pox.

Or it might be measles, in which case you need to know—fast—because measles is the most contagious disease on earth. Among unimmunized people exposed to the virus, 90 percent will contract the disease. And each of these people will spread it to twelve to eighteen others in an unvaccinated community. Complications like pneumonia and meningitis can be permanent, deadly or both, especially for immune-compromised patients such as those with cancer. And, in the ER, one of these kids might be in the next bed.

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Older Americans remember measles as a common childhood disease that just had to be suffered through, but it is still frequently deadly in low- and middle-income countries. In 2014, an average of 400 kids died each day of measles, most under the age of 5. In the current US outbreak, 20 percent of patients were hospitalized in California during the first six weeks of the year. And one in fifteen kids will develop more serious complications, such as severe pneumonia, otitis media with the possibility of permanent deafness, and acute encephalitis. The cruel, late complication of subacute sclerosing panencephalitis (SSPE), a progressive brain disease, is inevitably fatal. In Germany, which has seen an explosion of measles for reasons similar to those in the United States, twenty-seven children died of SSPE between 2005 and 2010. One teenager died of SSPE just last year.

So a doctor needs to be able to diagnose measles at “hello,” not wait for the results of two blood tests taken two weeks apart while the child spreads measles, as happened at Disneyland. And, as I rapidly realized, using Koplik spots as a diagnostic aid is better suited to passing exams than clinical practice. Toddlers with measles tend to be extremely irritable and not wildly eager to open their mouths on request for viewing. Nor would you want to get that close if you were uncertain whether you had been immunized.

The crucial question thus becomes: Cough, or no cough? If there’s no cough, it’s not measles. Period. Which is good, as excluding measles early averts both parental and departmental panic. But if an unimmunized child or adult is coughing, take it very seriously. Ensure that the child is kept away from places where he or she could spread the disease. Educate parents on how to treat the symptoms. And get the child out of the ER as quickly as possible before he or she infects other patients and staff.

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These steps have become particularly vital now that measles, long forgotten, is back in the United States. After disappearing in 2000, it has re-emerged alongside nasty allegations about the danger of the vaccine by anti-vaccination ideologues and unscrupulous politicians, even though the vaccine is safe, and mass measles vaccination is the single best public-health intervention we have.

As doctors, we know a few things that are fundamental to our well-being. Most of these are public-health measures that enable us to live much longer and better lives than people did 200 years ago. These measures of mass salvation include water purification, toilets and sanitation, garbage collection and disposal, nutrition and vaccination to protect children from infectious diseases like smallpox, polio and measles.

Smallpox was a truly nasty disease, with a fatality rate of 30 percent. Its eradication was the result of achieving global herd immunity, a feat of international cooperation and cost-effective investment in a global good. Herd immunity comes from mass vaccination and eliminates the virus. It protects the entire community, particularly children and adults who can’t safely be immunized, as well as babies too young to be vaccinated. When the global campaign began in 1967, there were 10 million to 15 million cases of smallpox a year. Places that had attained herd immunity, such as Europe and North America, had to maintain it to prevent imported cases from India and Africa from triggering an epidemic while mass vaccination campaigns created global herd immunity. Ten years later, the virus died out. Smallpox eradication is the public-health success story of the twentieth century, and because of it we are now determined to try to eradicate other infectious diseases, such as polio and measles.

Polio, perhaps the most frightening disease of the twentieth century, because of its invisible spread and devastating effect, crippled tens of thousands of children each year before the discovery of a vaccine sixty years ago. Americans can be rightly proud of the March of Dimes, an enormous effort driven by American mothers, which raised tens of millions of dollars to find a vaccine. The global campaign to eradicate polio required massive international cooperation, overcoming Cold War divisions, to bring the number of global polio cases today down to a few hundred a year.

Measles, like polio and smallpox, is a horrible disease. Second only to smallpox in the total number of deaths it has caused over the past two millennia, it’s still a major killer of young children in the developing world. The creation of a vaccine was widely welcomed. It is usually delivered jointly with vaccines for mumps and rubella, known in combination as MMR. Two shots provide 99 percent protection and lifelong immunity.

But because of vaccination lapses, measles is now on the rise. There were twenty-three separate outbreaks in the United States in 2014, involving 644 individual cases—a record number since measles was eliminated from the United States fifteen years ago. So far in 2015, there have been 170 cases in seventeen states and the District of Columbia, 74 percent of which are linked to Disneyland. Blaming it on Mexico and porous borders, as some opportunistic politicians have done, has no basis in reality; there were only two cases in Mexico in January, both imported from the US. Globally, the number of deaths rose from 122,000 in 2012 to 146,000 in 2013, reversing a twelve-year downward trend. In November 2014, the World Health Organization gave up on meeting its target for measles control.

And it gets worse. Measles is so contagious that it is used as the indicator disease to show deficits in immunization coverage of all vaccine-preventable diseases—which means the problem goes well beyond measles. We are now seeing outbreaks of whooping cough in the US, mumps in Britain and tuberculosis more widely. Just last year, the WHO announced a public-health emergency of international concern for polio.

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Why is this happening? In Syria, the government’s effort to withhold childhood vaccinations in areas considered politically unsympathetic to the dictatorship was one reason for the popular uprising. Small wonder that polio returned to that country, and that, according to available data, there were over 10,000 cases of measles there in 2014. Parents are desperate for vaccines, and last year medical workers braved Bashar Assad’s barrel bombs to vaccinate 1.4 million children in northern Syria for polio, achieving 92 percent coverage. Similarly, in West Africa, people are begging for Ebola vaccines. Yet in the United States, the anti-vaccination movement has seen increasing numbers of parents refuse measles and other vaccines “on behalf” of their unprotected children.

That misguided movement began with the unconscionable malpractice of Andrew Wakefield. A doctor who has since lost his license, he and his co-authors of a 1998 article in The Lancet made up a syndrome consisting of diarrhea and developmental disorder (“regressive autism”) that he tried to link to the MMR vaccine for the purpose of financial gain. He was not at the time a practicing doctor, and had no expertise with autism, but he manipulated parental fears and an editor’s penchant for controversial papers to secure publication in a respected journal. Extraordinarily, despite a financial conflict of interest, despite the fact that he’d fabricated the syndrome and falsified data to fit his criteria, his paper passed peer review.

That paper was then used to support litigation against three companies that produced the MMR vaccine, and to lobby for use of Wakefield’s own measles-only vaccine. Wakefield went on to make over $600,000 in fees alone from the lawyer who brought the lawsuit.

In his 1998 paper, Wakefield alleged that eight children developed autism six days after receiving the MMR vaccine. I remember the paper well, because I was a pediatric fellow in London at the time. I and every other pediatrician were immediately besieged by parents demanding measles-only vaccines. We were staggered by Wakefield’s ridiculously small, uncontrolled and clearly biased study about a syndrome that none of us had heard of, even though the MMR vaccine had been widely used since 1968. But it was also hard to imagine that The Lancet would publish something with such obvious global ramifications unless there was irrefutable scientific evidence uncontaminated by financial interest.

It took six years for The Lancet to admit Wakefield’s financial conflict of interest, but it did not retract the paper until 2010. Meanwhile, the rise of measles in the United States, the United Kingdom and other parts of Europe reflects the damage done; in February, a toddler died in Berlin amid the biggest outbreak in years. And the consequences extend well beyond the West. In Nigeria, Ebola was successfully stopped in 2014, and polio is close to being eliminated, yet this country has the second-highest number of kids not vaccinated for measles, after India. Among the reasons Nigerian parents have been known to refuse to vaccinate their children is that they are familiar with the anti-vaccine movement incited by Wakefield. If American parents aren’t vaccinating their children, why should they?

Vaccination rates of 94 percent are needed to prevent measles transmission in high-risk areas like childcare centers and schools. Yet in Orange County, California, and West Hollywood, many schools have childhood immunization rates of less than 92 percent, with some schools having rates as low as 38 percent—levels seen in developing countries. The Lancet could help now by publishing an unequivocal editorial discarding the myth once and for all.

Using vaccination as a political tool is contrary to the public good. Yet some politicians seem unable to assert collective responsibility over individualism: Chris Christie dithers about balancing parental choice and public health, while Rand Paul offers uninformed opinions. A White House spokesman said that “people should evaluate this for themselves,” though he urged a bias toward “good science.” Seriously? Should we also start debating the value of safe drinking water and sanitation?

In medical school, I couldn’t see myself in a career in public health, which seemed like a “done deal” whose value was obvious. But I returned to it a convert after ten years as a critical-care pediatrician. Kids are the most vulnerable, with their poorly developed immune systems. They are also the most vulnerable to the politicization of the public good, the only ones without a direct say in the debates about their welfare.

Parents are understandably confused, but rising polarization isn’t helping. Amid the controversy, it’s easy to miss the point: a very serious disease is getting on with its job of invading, infecting and re-colonizing the country, and we are losing control of it. The “herd” can afford an occasional, unvaccinated free-rider, but when large numbers of people place their own ideologies and idiosyncrasies above public health, it is children who suffer the consequences.

It is particularly because of these children that we need to take infectious disease more seriously. And in an increasingly crowded and connected world, we need to think of public health not simply locally but globally. Air travel means it is impossible to stop viruses from spreading around the planet, and building the homeland walls higher won’t help; the only reliable antidote is global public health. We have to pay attention to the neglect of infrastructure in West Africa, where Ebola erupted, and the Syrian military’s deliberate destruction of public-health systems in opposition-held areas, where polio emerged. Middle East respiratory syndrome now threatens from the Persian Gulf. All of these diseases can easily spread to the West, with profound implications. Just look at the effect of a few cases of Ebola in the United States.

If the threat of measles isn’t enough for you to reject anti-vaccination folklore, here’s a little-known fact about the benefit of vaccination. The measles vaccine doesn’t only protect against measles. Because it contains a small amount of a live virus, the immune system must rev up to fight it, which in turn reduces mortality from other infectious diseases—including pneumonia and sepsis—by 50 percent. This protective effect lasts until a vaccine is administered with a killed rather than a live virus, such as the one for diphtheria and tetanus. So do you want to protect your kids? Give them the measles vaccine.

And all of us should get educated. Education is a social vaccine against the sustained ignorance that blocks effective responses to public-health threats. But education alone is not sufficient to overcome self-interest. We all need to act for the public good. Individuals and institutions that are allowed to prioritize personal preference or financial and political gain ahead of children’s health are irresponsible and unethical, and they should not call the shots. In the short term, children’s health and lives are at risk; in the long term, we jeopardize the local and global control of these previously conquered diseases. Prevention is not only better than cure—which isn’t an option for most of these diseases—it’s also more cost-effective.

Our common desire to protect children’s health was always the best reason to eliminate these diseases, and it remains our best hope for bringing us all back to common ground. Let’s not allow spin doctors and myths to prevail over our shared aim of shielding the world’s children from the world’s oldest and deadliest diseases.