As epidemiologists, we have two goals. The first is to prevent. When that is not possible, the second is to minimize disease and extended disability. Toward that end, we deploy an arsenal of medical countermeasures.
We have several important weapons for prevention: sanitation, including safe water and food and the safe removal of human and animal feces and urine; vaccination; and anti-infectives, which can minimize disease, disability, and, potentially, infectiousness. Vector control is critical for reducing disease-transmitting mosquitoes, ticks, and flies. Then there are ancillary measures, such as disinfecting agents, and infection control in hospitals, nursing homes, and daycare facilities. And there are nonmedical actions, too, including education, attempts to get the public to change certain behaviors, public communications, and quarantine. Guidance on sexual habits and precautions for multiple-partner activity are examples. So is changing burial practices for Ebola fatalities, as we learned during the 2014 outbreak in West Africa.
But the fundamental tool of epidemiology has always been, since long before we had a scientific method for identifying microbes or a germ theory of disease—and, I expect, will always be—observation.
In rural England, by the eighteenth century it had been observed and noted that milkmaids seemed generally to be immune from the scourge of smallpox, which had a mortality rate of at least 30 percent, and often significantly higher. Dr. Edward Jenner speculated that exposure to the similar but far less serious cowpox somehow protected them. In May of 1796, in a now legendary experiment, he took pus from cowpox blisters on the hand of milkmaid Sarah Nelmes and scratched it into the arms of James Phipps, the eight-year-old son of his gardener. James developed a fever and didn’t feel well for a short time, but he soon recovered. When Jenner then injected him with pus from actual smallpox lesions, the boy remained disease-free.
Jenner published three papers on the subject and thus became the father of vaccination—the fundamental weapon in the armament of public health. And it began with careful observation.
John Snow, an English physician born in 1813, is considered the patron saint of epidemiology and public health. A member of the Royal College of Surgeons, Snow was a pioneer in the safe administration of anesthesia and administered chloroform to Queen Victoria during the birth of her last two children, in 1853 and 1857.
In those times, London suffered every few years from outbreaks of cholera, which sickened, killed, and spread fear throughout the metropolitan area. The prevailing belief in the medical community was that the outbreaks were caused by “miasma,” or bad air. Snow was skeptical and published his doubts in an 1849 paper titled “On the Mode of Communication of Cholera.” At the time, microbiology was in its infancy and the bacterium that caused cholera had not yet been discovered. That discovery would occur over the course of a series of studies and publications by Filippo Pacini, an Italian physician, between 1854 and 1865.
The outbreak of August 1854 was the worst in memory, and in some parts of London the mortality rate exceeded 10 percent. One of the most severely hit precincts was Soho, an area of the West End bordered by Oxford and Regent Streets that had seen a large influx of immigrants and the poor and had inadequate sanitation and virtually no sewer facilities.
Snow realized that the largest cluster of cases appeared to be concentrated in a two-block-long thoroughfare in the middle of Soho, near Regent (now Oxford) Circus and along Broad (now Broadwick) Street. He began recording these clusters by blackening out the buildings in which the residents lived on a London map. With the help of Reverend Henry Whitehead, assistant curate of St. Luke’s Church and, at the time, a believer in the miasma theory, Snow then went to the homes of the afflicted and asked them about their personal habits and whereabouts in the days before they became ill.
Through this method of shoe-leather epidemiology, Snow came up with an astonishing observation. Nearly all of the victims had taken water from the Broad Street pump. What’s more, of the ten deaths mapped closer to another pump, five of the victims had still used Broad Street because they preferred the water. In three other cases, the dead were children who attended school near Broad Street.
Snow viewed samples of the pump water under his microscope and subjected them to chemical analysis. The results were inconclusive. But he was by then so convinced of the association that on the evening of September 7, he went before the Board of Guardians of St. James’s Parish, detailed his statistics, and requested that they remove the pump handle, rendering the pump inoperative.
The next day that is just what they did. Though cholera was already waning as many fearful Londoners fled the city, the shutdown of the Broad Street pump effectively ended the outbreak.
Unfortunately, after the cholera crisis was over, government officials gave in to local residents who wanted their well back and replaced the pump handle. It was only in 1866, when a similar cholera outbreak associated with drinking water from another contaminated well occurred, that the Broad Street pump was permanently closed.
Today, the John Snow pub, on the corner of Broadwick and Lexington Streets, is a place of pilgrimage for any epidemiologist or public health officer visiting London. I have been there many times and shared a pint or two. Each time I visit this landmark, I’m reminded that even though scientific research had not yet established the cause of cholera, the basic methods employed by Dr. Snow remain the foundation of epidemiological investigation to this day.
Snow’s work was clearly an important milestone in epidemiology and public health practice. But I believe the honor of being considered the father of modern public health could go to Nikola Tesla.
Tesla was the Serbian engineer credited with inventing the alternating-current induction motor and widely applying the use of electricity. The advent of electricity brought about quantum leaps in public health and infectious disease control. With electricity and water pumps, safe water supplies could be realized throughout the world. And with running water, effective sewer systems could be put into place. Electricity also brought us refrigeration, the ability to pasteurize milk, vaccine manufacturing, and air conditioning to keep mosquitoes out of our homes and places of work. It revolutionized medical practice through the invention of X-ray and other imaging technology, diagnostic equipment, mechanical ventilators, and more.
In 1900, the average life expectancy in the United States was forty-eight years. By 2000, just one hundred years later, it was seventy-seven. For every three days we lived in the twentieth century we gained a day of life expectancy. Consider that in light of the fact that early humans in the form of Homo erectus emerged 2.4 million years ago, and it took us until 1900 to achieve our forty-eight-year life expectancy. That means it took 80,000 generations to reach the 1900-era life expectancy, and only about 4 to reach our current level. With clean water, sewer systems, safer food, pasteurized milk, and vaccines, we made historic advances in eliminating the diseases that killed children, who are particularly vulnerable to the illnesses related to these environmental conditions.
But lest we start congratulating ourselves too enthusiastically for our progress, as we shall see, the challenges we face going forward are, if anything, even greater than those we faced in the past.
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TAMPONS
On June 27, a second MMWR report summarized the results of a case-control study that included fifty-two cases—many of which were included in the May 23 report—and fifty-two age- and gender-matched controls. This is a type of epidemiologic investigation where we interview the cases—or the case’s family members if the case is too sick or has died—using a comprehensive questionnaire to systematically learn about every possible relevant factor in the case’s life that could have played a role in her illness. Then we identify “control” participants: people who are closely matched with the case individuals, for example, by age, gender, and residence, but have not been ill. We interview them using the same questionnaire. Our analysis compares the frequency of factors present among the cases and controls to determine if there are differences that can help us explain why the cases became ill.
That analysis found a statistically significant association between tampon use and TSS; in other words, the difference in tampon use between the cases and controls was very unlikely to happen by chance alone, with a much higher number of cases using tampons compared to controls.
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Ironically, shortly after the CDC announcement on September 19, the American College of Obstetricians and Gynecologists speculated publicly that it was a personal hygiene issue and recommended that menstruating women change tampons more frequently.
This turned out to be exactly the wrong advice. By telling them to change their high-absorbency tampons more frequently, the college was putting women at higher, rather than lower, risk. The more frequently a woman changed her high-absorbency tampon, the more oxygen she introduced into her vagina. Another lesson I learned from my experience investigating TSS is that if you don’t know what you’re talking about, then don’t talk, or at least say you don’t know. Yes, women wanted and needed sound and timely expert advice about the use of tampons, so it’s understandable why the American College of Obstetricians and Gynecologists felt the need to make a statement. But the only real information they had at that point supported not using tampons at all.
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As we have seen with HIV/AIDS, toxic shock syndrome, and Brainerd diarrhea, virtually nothing that happens in life is off-limits or irrelevant to the epidemiologist’s purview. It ranges from the most intimate and personal aspects of individual biology all the way up to the most public and far-reaching geopolitical clashes.
The lesson the Brainerd experience taught me was: You don’t have to have all the answers to have the critical answer. Like John Snow, we can stop or limit the occurrence and impact of infectious diseases without knowing everything about them. I often hear that we can’t act on this or that because we don’t have all the answers. That’s nonsense. We have to be prepared to go into battle with the knowledge and resources we have, beginning with basic observation.
And we can!
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