Circulating Now welcomes guest blogger David Morens, Senior Associate at the Johns Hopkins Bloomberg School of Public Health and Senior Advisor to the Director of the National Institute of Allergy and Infectious Diseases (NIAID). Dr. Morens is an epidemiologist with a long-standing interest in emerging infectious diseases, virology, tropical medicine, and medical history.

Since mid-December 2014, epidemic measles has spread from Disneyland to infect 170 Americans in 17 states/jurisdictions. People who remember life in the 1950s, when Disneyland was built, also remember measles. In those days, almost every kid got it: the fever, the cough and runny nose, the awful red blotches that kept you out of school and home in bed. Some kids even died from it, or got encephalitis, or eye damage. But beginning in 1963, measles vaccines ended all that. The nation-wide measles epidemics that swept the U.S. every 2–3 years were stopped cold. Why then do we still have measles in 2015?

First, some history. The initial advance against measles occurred over 1,000 years ago, when Persian physician Mohammad-e Zakariā-ye Rāzi (ابو بكر محمد ابن زكرياء الرازى, or “Rhazes”) wrote al-Judari wa al-Hasbah (On Smallpox and Measles), describing and distinguishing these two diseases. Before the development of germ theory, there was little appreciation that one disease differed from another. Full clarification of this important distinction awaited discovery of viruses and microbes, centuries later. But Rhazes helped lay the groundwork for its appreciation and acceptance.

Beginning in the Renaissance, measles (also called Masern, morbilli, rubeola, rougeole, and many other names) became known to parents as one of the deadliest of the childhood fevers. In 1713, for example, measles killed 45% of persons infected in the household of Puritan minister Cotton Mather, including Mather’s wife and three of their children, roughly the same fatality rate as the 2014–2015 Ebola epidemic, and almost as terrifying.

Mather was then the New England colonies’ foremost medical authority. Sometime before 1714 he had learned from an African-born slave that smallpox could be prevented by inoculating fluid from the blisters of infected persons into the skins of persons who had not yet been infected. Similar stories reached Europe from Turkey and elsewhere, among the most astonishing medical stories anyone had ever heard. When a smallpox epidemic came to Boston in 1721, Mather, along with the young Benjamin Franklin, Franklin’s brother, and others, campaigned successfully in favor of smallpox inoculation. Inoculation saved many lives between then and 1798, when it was replaced by an even more radical, but safer procedure: vaccination.

The prevention of smallpox by inoculation had no scientific explanation: it just worked. But that got people thinking. In 1758, Scottish physician Francis Home (1719–1813) reasoned that if inoculation worked to prevent one of the pair of diseases described by Rhazes, the same method might work against the other. And in a 1759 publication, Home showed that measles could also be prevented. Whether by insight or blind luck, he chose, as the inoculum, blood from children at the height of their illnesses. In retrospect, those early smallpox and measles inoculation studies, and Jenner’s later vaccination studies, were the first experimental demonstrations of what we now understand as active immunity. Just like natural diseases, fluids from infected people or animals, inoculated into others, can confer long-lasting protection. And that is the basis of modern disease prevention via inoculation, vaccination, passive immunotherapy, and protection of newborns by maternal antibody.

Home’s method was never widely adopted, perhaps because of the expense and difficulty getting blood from sick children for the inocula (parents often refused). Control of measles by immunization had to wait two centuries, until the era of modern virology. Tissue-culture propagation of viruses—for which Enders, Weller, and Robbins were awarded the 1954 Nobel Prize—led to the development of the first measles vaccines, which were introduced in the U.S. between 1963 and 1967. In recent decades, these vaccines, brought to every country of the world, have saved millions of lives. There has been a five- to ten-fold drop in annual global measles deaths in the past 15 years, a tremendous achievement that brings us to the doorstep of measles eradication.

However, measles does not go quietly. Politics, superstition, and irrational fears prevent some parents from vaccinating their children. Some believe that measles itself is relatively harmless, and that the vaccine causes diseases like autism—despite overwhelming evidence to the contrary. Some parents even take their children to “measles parties” to purposely expose them to measles-infected children, putting their children at risk of severe or fatal disease—a risk that is, by rough calculation, over a hundred million-times greater than any complication arising from measles vaccination. All of which goes to explain why we are now having an American measles epidemic. If current public health campaigns can persuade parents to have their children vaccinated, one day measles can be eradicated, just like smallpox.

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