Epidemics in Western Society Since 1600

HIST 234 - Lecture 14 - The Germ Theory of Disease

Chapter 1. Germ Theory of Disease [00:00:00]

Professor Frank Snowden: Well good morning. I think we should get started. And what we'll be talking about this morning is the germ theory of disease. In a sense, it's taken us half a course to reach a period when we begin to see the development of what you would probably recognize as a scientific modern medicine. To appreciate the enormity of what happened with the germ theory of disease, I think it's worth casting our eye back to a point we had already reached.

Let's say we compared the year 1789 with 1900. Before 1789, and the developments with the Paris School of Medicine, you'll remember the conceptual framework was dominated, still, by that of Hippocrates, Galen and humoral medicine. Humoralism was in retreat, as doctors were absorbing ideas about the circulatory system, and the nervous system. But the medical philosophy, the vocabulary, therapeutics and medical education, were still cast in the old framework, supplemented by other developments — astrology, for example — and epidemic diseases were thought to be explained by the doctrine of miasma — that is, the corruption or poisoning of the air — or malaria, as it was called at the time.

By 1900, I think it's clear that more change had occurred than in all of the centuries since Hippocrates combined, and that medical science, whose basic principles were recognizably similar to our own today, had emerged. Furthermore, the speed of change was gathering momentum as the nineteenth century progressed. The closing decades of the century witnessed a wholesale revolution, with the germ theory of disease as its central feature. This theory, I'm going to argue, was as important a revolution in medicine as for, example, Galileo's theory of the rotation of the earth was to astronomy; or perhaps Darwin's theory of natural selection was to biology; or gravitation to physics.

So, what I would like to begin with then is looking at what is the germ theory? What were its preconditions? Who were the decisive figures? What were the decisive events associated with that famous trio of Louis Pasteur, Joseph Lister, Robert Koch? What were the implications? Let's avoid the idea of a single genius coming up with a great idea. Let's question the vision behind the idea of the Nobel Prize. I'm going to be arguing that these discoveries, that culminate in the germ theory, had a long gestation period, and were a collective process that required a long train of preconditions.

Chapter 2. Preconditions [00:03:33]

Let's look at the preconditions first. I'll argue that they're conceptual, technological and institutional. Let's look at conceptual preconditions. The germ theory of disease didn't arise directly out of hospital medicine and the Paris School, but I think it's inconceivable without the background of that development. It was crucial to have a nosology — that is, disease classification — the idea of disease specificity — that they were specific entities — and without the idea of localism; that is, lesions. And also essential was the new development of pathological anatomy, derived from the post-mortem in the Paris hospitals.

The idea of specificity was critical. Any further progress to the idea of a microbial disease depended on the view that diseases didn't transform from one into another. Before the Paris School, it was common to believe, for example, that cholera — to take one disease — was simply a heightened form of endemic summer diarrhea. It wasn't a specific disease, and it grew out of another preexisting condition. The germ theory depended instead on the conviction that there are stable, unchanging disease entities, that each one is specific and has a specific microbial cause. But the followers of Louis — Pierre Louis, that is — in Paris, while carefully distinguishing one disease from another, and classifying them, didn't advance much towards the idea of the causative pathogens behind them.

Now, when we've talked about the Paris School, I don't want to give you the idea that all of the crucial figures in disease specificity, and nosology, were French. There were other crucial figures as well. William Gerhard, who distinguished typhus from typhoid. He had studied in Paris with Louis for a couple of years, and then returned to his native Philadelphia. During an epidemic of typhus, he dissected hundreds of cadavers and discovered that their lesions had no resemblance whatsoever to typhoid.

There was William Budd, who wrote an important book called Typhoid Fever: Its Nature, Mode of Spreading and Prevention, in 1873. And he referred to the unchanging, specific nature of the disease. Let's listen to what he said. He said this: "To propagate itself and no other, and that on a series of indefinite progressions, constitutes the very essence of the relation on which the idea of species is founded. How much this applies in the animal and plant world we all know. It is strange that what it implies, in the case of diseases, should be so seldom recognized until now."

Or there was Pierre Bretonneau, who believed that there were morbid seeds that caused special diseases, just as every seed — in the natural history, that is — gives rise to a determined species. And he applied that idea to diphtheria. Just so as apples don't turn into wheat — apples seeds into wheat — so too endemic diarrhea doesn't transform itself into Asiatic cholera. There was an important transitional figure too. Claude Bernard, of the Paris School, one of its stars, who lived from 1813 to 1878, and in 1865 wrote an important book called An Introduction to the Study of Experimental Medicine, where he presented a critique of the Paris School. He argued that diseases were dynamic processes. They weren't static in the way that the Paris idea of nosology seemed to suggest. And he argued that they, hospitals, displayed the end stages of diseases, not their beginnings. And he argued that hospitals and clinics had an excess of variables that wasn't helpful for the further development of medical science. So, he proposed an alternative, that was embodied in his title; that is, experimental medicine. And by that, he meant laboratory medicine. He's one of the people who suggest a new epistemology for medicine, which isn't the hospital ward but the lab, where you could have the experimental testing of single variables in controlled settings. Here was a new source of medical knowledge.

If that provides conceptual preconditions, there were also institutional ones. And here I'm thinking of the rise of the laboratory, of the university; that is, full-time professional scientists, research institutions, and Germany leading the way, rather than France, in this development. There were also technological foundations. It's impossible to think of the rise of the germ theory of disease without microscopy. And so it was indebted to Anton van Leeuwenhoek, who lived from 1632 to 1723, and developed the simple microscope. And then in the 1820s, and thereafter, there were major improvements: the development of the compound microscope and higher magnification, the work of the Zeiss Company and the development of lenses.

There was also, for a fourth precondition, a lonely, neglected pioneer, and that was a Hungarian gynecologist, who lived in Vienna, called Ignaz Phillip Semmelweis, whose crucial idea, which dates from the 1840s — Semmelweis noted that the infection rate in childbirth was much lower on obstetrical wards where women were delivered by midwives, rather than on wards where they were delivered by physicians. The reason had nothing to do with their training or relative degree of benevolence and malevolence. The point was that the physicians were just returning from post-mortem examinations, from autopsies, after which, at that time, they didn't wash their hands, and so they were transmitting disease to their patients, from autopsies they were performing in an adjacent building.

So, Semmelweis, suspecting — although he didn't know the mechanism — that this was the case, established elaborate hand-washing rituals, using a chlorinated lime solution — a little bit the first hand sanitizer, we might say — and he noted that mortality plummeted from twenty percent to one percent. Unfortunately, his own career was not a happy one. He was mocked by his colleagues as a charlatan, and was actually demoted in his own hospital. Well, then, there's a fifth precondition, and that's the development of the basic sciences. And it's hard to imagine, as we'll see in a minute, the rival of the germ theory without chemistry in particular.

The specific issue that gave rise to the germ theory of disease was fermentation. And Pasteur, after all, was originally a chemist, who in the 1860s became a biologist, and we should note that he wasn't a physician. This is to introduce you to Louis Pasteur. The immediate background to the germ theory of disease involved the dominant theory of the day, which was called the zymotic theory of disease; that is, that it was a form of ferment — a little bit like Pettenkofer had asserted — caused by some fermentation of decaying organic material. Under the right conditions of soil, temperature and moisture, this fermentation would give off a poison into the environment.

Also quite widespread was the idea of spontaneous generation, that diseases arose somehow spontaneously in a particular locality, weren't brought in or imported from the outside. There was a famous experiment about this, from the seventeenth century. It was Redi's maggot experiment. The idea was that if you could have rotting meat, and you could cover it, you wouldn't develop maggots. But if you didn't cover it, then you would find that it was full of maggots. So, the maggots didn't appear in the rotting meat by some internal mechanism of spontaneous generation, but were imported from outside. And Pasteur, as we'll see in a minute, takes up this very idea, to the idea that germs too, like the maggots, are imported from outside.

Chapter 3. Louis Pasteur [00:14:34]

The immediate issue for Pasteur was in fact fermentation. He began by studying the fermentation of wine and beer, and in particular their spoilage. At the time, this was thought, when he took up his work, to be a chemical process. And remember that Pasteur was not a physician but a chemist originally. Well, what he did was to discover that the fermentation was caused instead by living microorganisms, bacteria that he identified through the microscope. Now, this was a high-profile investigation in the 1860s, for the simple reason that the production of wine and beer involved two of France's major economic activities.

Pasteur — and this was part of his genius — immediately made a far-reaching connection. In his estimate, the fermentation that he saw in wine and beer, now caused by bacteria, was analogous to putrefaction and infection in wounds, for example. So, he began to regard disease as a process involving microorganisms, living things. This was work that Pasteur conducted in the late 1850s and 1860s, and it marked the first transformation in his career from that of a chemist into a biologist, or we might say today a microbiologist. He examined not only wine and beer, he then turned his attention to milk and its souring, and he wrote a book on that, and then a study on wine and a study on beer.

Now, of great importance was the fact that Pasteur's discovery that abnormal fermentation leads to spoilage, along with that went another discovery he made, which was that this process could be controlled by heat. Here was a major public health discovery, and that led to the process we now know as pasteurization. So, already in the 1860s, Pasteur was busily transforming biology. Even if had he stopped then, his discoveries were already those of a fully productive life's work. But then in the 1860s came a turn in Pasteur's interests from biology, more specifically to medicine and public health. And he began to study spontaneous generation. Now, followers of Pasteur believed instead in biogenesis.

With regard to cholera, that we already examined, about which there was a debate, the idea was that cholera was imported from outside. It didn't arise spontaneously. It wasn't the transformation of some other disease that already existed into cholera. Rather it was a specific disease that could not arise as a heightened form of a pre-existing condition. Pasteur also devised — well, Koch didn't think this was so elegant, but it certainly convinced Pasteur and his followers — a famous swan neck flask experiment. That is, he sterilized a flask with a swan's neck, and found that if the culture is boiled, and the flask prevents air from gaining access to it, then there was no development inside of organisms that we would call bacteria. A culture of them could grow in the flask, only if germs were allowed to enter it. But if the neck of the flask is broken and air is emitted — you can see the neck broken at the bottom — then you get a luxurious development of life. And this had enormous implications for diseases and wounds.

Pasteur wrote simply, "There is no known circumstance in which it can be confirmed that microscopic beings came into the world without germs, without parents similar to themselves." Now, Pasteur's success was partly based on the fact that he was aware of the full range of the scientific implications of his work, and he selected carefully topics with high profile, philosophical and biological interest. He was an expert at cultivating the media. That was one reason that spontaneous generation had led to so much excitement. But most decisive in Pasteur's work was what he did in the 1870s, as he turned to diseases, demonstrating the full implications of his ideas on fermentation in the previous decade. This new phase of discovery occurred, despite the fact that in 1868 he suffered a major cerebral hemorrhage, that left him paralyzed on his left side.

What did Pasteur do in the 1870s that was so crucial? Well, first of all, I'll look at two major things that he did. One is work with silkworms, and the other is work with chicken cholera and anthrax. The first thing was a major contribution to the germ theory of disease, accomplished by the work with an unexpected experimental animal; that is, the silkworm. And again let's look at the fact that Pasteur's success, his influence and his genius, was in part the fact that he took on really high-profile research topics; that is to say, disease of silkworms, where these diseases were decimating one of France's leading industries, that is, silk.

Through meticulous and painstaking research, Pasteur demonstrated that there were two major diseases at work affecting France's silkworms. He called them pebrine and flacherie — you needn't remember them for our purposes — and asserted that both were specific diseases caused by bacteria. And he immediately realized that there were enormous implications, not only for silkworms, but for human beings as well. He isolated then two germs affecting silkworms, and demonstrated that they were responsible for specific contagious diseases.

Pasteur isolated a germ and convincingly linked it with a specific disease, and the concept of specificity was at the basis then of the whole idea of the germ theory of disease. Now you know Pasteur didn't invent the idea of contagion. You've seen it with Fracastoro. You've seen it in John Snow, who talked about the possibility of animalcules. And there were other scientists — Casimir Devaine in France, the English physician John Sanderson — who were also advancing a hypothesis that they were finding microbes with their microscopes, and hypothesizing that they might be the agents of disease. But Pasteur was the first to provide a demonstration in a specific case, proving that microbes were the causative agents of specific diseases, and he provided a methodology for further experimentation and discovery.

Pasteur then turned from silkworms to diseases, the diseases of chicken cholera and anthrax. Neither is responsible for extensive human disease, as both are causes of diseases of animals. But what was critical was the process. His work on anthrax helped to establish a model for investigating infectious diseases, and establishing the claims for the germ theory of disease, and putting that on solid foundation. At the same time, he made another major development. His vision went beyond simply demonstrating the germ theory, although he did that. In addition, he developed a public health practice — that is, vaccination, which had been pioneered a hundred years before — and he helped now to found the discipline of experimental immunology.

Chapter 4. Attenuation [00:24:17]

Now, let's — we've seen vaccination and the work of Edward Jenner. Let's define. Vaccination is the introduction into the body of either the whole, or part, of a disease-causing microorganism, in order to teach the immune system to attack that same organism, should it reappear in the body through natural processes. The mechanism is that the vaccine primes the immune system to produce antibodies, or teaches immune cells to recognize and attack the organism, that we now know perhaps to be a virus, a bacterium, or a parasite of a different kind. The problem, of course, was how to stimulate immunity without causing disease. Jenner benefited from the cross-over immunity from cowpox to smallpox. Pasteur did something else. He used the concept of attenuation.

Jenner is the father of immunology, in a sense, Pasteur the founder of experimental immunology. The idea he had was that live pathogens could be introduced in the body, but only after being treated in some way — heat, for example, or passage through a different host first was another — in such a way then that their virulence is diminished. Then they'll stimulate the immune response, without causing disease at all, or only a mild disease.

This discovery was made during his work with the bacterium that causes chicken cholera, made sort of by chance — serendipity played a role. He left a batch of bacteria untouched for a week or so while he went on vacation during the hot summer months. On returning, he found initially, to his frustration, that the culture no longer produced the disease when he attempted to infect other chickens. So, he got a fresh batch of bacterium, and injected the same chickens with it, as well as a lot of new chickens, and made a surprising discovery. That the original chickens, injected with the old vaccine, remained healthy — in our terms, they were immune — while the new and previously untreated chickens sickened and died. He repeated the experiment several times, with the same results, and concluded that the summer heat had changed or attenuated the culture of the bacterium.

Later techniques expanded the repertoire, demonstrating that heat could kill vaccines of chicken cholera but still induce immunity. There were other vaccines that could employ live but attenuated bacteria or viruses. Some used killed microorganisms. Some used sub-unit vaccines. And the processes of attenuation are not only heat, but let's say for polio, could be the passage through formaldehyde and various — there are other means. Attenuation though was critical to the development of vaccine as a public health strategy. But let's return to Pasteur. Having discovered attenuation with chicken cholera, Pasteur applied the same principle to the different disease of anthrax. The pathogen responsible was the Bacillus anthracis that had recently been isolated by Robert Koch. And if you see the film, The Story of Louis Pasteur, you'll see what he did in 1881 with the bacterium.

In a famous experiment, he vaccinated twenty-four sheep with an attenuated — that is, heated — bacterium, after which he challenged the original twenty-four sheep with live unattenuated anthrax injections, as well as twenty-four control sheep that had not been vaccinated. The vaccinated sheep remained healthy. The non-vaccinated all died. Then came the 1880s, and Pasteur turned to another high profile disease, and that is rabies. Having discovered attenuation by heat, with chicken cholera and anthrax, Pasteur extended the principle of attenuation by other means. This involved further famous experiments.

Rabies, as it turns out, was not another bacterial disease, but a disease caused by what we now know to be a virus. In this case, he attenuated the virus by isolating it from foxes, and then passing it through an unnatural host of a different species; in this case, the rabbit. So, passing the virus through a series of rabbit bodies, he succeeded in producing a variant that would no longer cause the infection in foxes, but would serve to protect against the natural occurring rabies. Rabies was not a high impact disease, in terms of numbers of people it affected, but it was a disease of high drama, and one that was then, and still is, universally fatal. So, it was ideal for attracting media attention.

The great human trial occurred in July 1885, with a famous case of a nine-year-old boy, Joseph Meister, who had been severely bitten by a rabid dog and was thought to be certain to die an agonizing death. But taking advantage of the incubation period for rabies, Pasteur vaccinated the boy with his attenuated rabies virus. Joseph Meister survived, and became a celebrity patient, the first person ever known to have survived after being severely bitten by a rabid animal. And Meister remained loyal for the rest of his life, to Pasteur. He returned, as an adult, to Paris, to work as a gatekeeper at the Pasteur Institute, where Pasteur himself was buried in the crypt. The apocryphal story — I won't assert its truth — the story is that he was killed in 1940, as an elderly man, when he tried to prevent occupying German troops from desecrating Pasteur's grave, the grave of a national icon of an enemy power. A slightly less poignant but better documented narrative is that he committed suicide in despair of the German occupation.

Well, the Pasteur Institute — that's the vaccination of Joseph Meister. It's not Pasteur doing the actual vaccination, because, as I said, he wasn't a physician. And this is the Pasteur Institute, founded in 1887, with Louis Pasteur himself as its first director, committed to biomedical research in Paris, and to a series of satellite institutes elsewhere in the world. It followed the public health strategy of vaccination, pioneered by Jenner, and now consolidated by Pasteur. The founding of this institute — you'll note its size and imposing nature — gives us the opportunity to note in passing another aspect of nineteenth and twentieth century science. The way in which it became a focal point for competing nationalisms, in a way familiar to us from the Cold War competition between the U.S. and the USSR. In any case, there's a clear case in the nineteenth century with the rivalry between Louis Pasteur and Robert Koch, the embodiments and icons of French and German medical science, of two hostile national powers. The Pasteur Institute in Paris rivaled the Koch Institute in Berlin. And that brings us — we'll also note the crypt where Pasteur is buried.

There's a kind of — what shall I say? — worship of Pasteur almost, and of French medical science.

Chapter 5. Robert Koch [00:33:28]

But let's move on to Robert Koch, who lived from 1843 to 1910, the second great figure in the establishment of the germ theory of disease, the German scientist who was twenty years younger than Pasteur. Now, if Pasteur's hallmark was the imaginative breadth of his scientific vision, Koch's distinctive feature was his scientific rigor, his more rigorous techniques of microbiology. He had a critique, a famous critique, of the whole swan neck flask experiment. He argued that Pasteur had been lucky — contamination was possible. He developed the plate technique, using the Petri dish and solid culture, and he developed staining techniques for microscopy.

What I'd particularly like you to note is his methodology, which he embodied in what are called "Koch's Postulates." This was the methodology for determining that a suspected microbe is the causative agent of a particular disease. He said you could know this under four conditions. First, the organism suspected as a pathogen must be found in all animals suffering from the disease. In other words, it has to be universally present where the disease is present. And then the organism must be isolated from a diseased animal, and grown in culture. Third, the cultured organism must cause the disease, when introduced into a healthy animal. And lastly, the organism must be re-isolated from the experimentally infected animal. These postulates are some of the most famous in medical science, and were the model for establishing germs as pathogens for other diseases.

Koch's microscopy had a number of immediate implications. His staining raised the idea that if you could stain, you could also have an idea of magic bullets, what later became antibiotics. But Koch didn't pursue that particular interest. The other was this led to reliable differential diagnosis, and therefore a more properly based nosology. It could lead also to major public health measures, and ultimately to developments in therapeutics. It furthered the sanitary idea, and gave it a firm, scientific basis, and irrefutably proved the truth of contagionism rather than anticontagionism, as Pettenkofer learned, to his cost. But immediately there wasn't — it didn't imply, and I think we should note this — the understanding of disease did not immediately lead to therapeutic advances.

Remember what happened in Naples during the cholera of 1884. Koch's idea was used for a very negative therapeutic method; that is, acid enemas that were administered to patients. Well Koch also moved forward on other diseases, applying the methods he had developed, that Pasteur had developed in the 1870s, and applying his own rigorous postulates. In 1882, the most famous of all, he isolated the bacterium that causes tuberculosis, the most prevalent disease of the time. The paper that Koch presented in 1882 was one of the most dramatic and important moments in the history of medicine. Tuberculosis was not feared in the same way cholera was, but it was unquestionably the greatest killer of the nineteenth century, and until 1882, it was shrouded in mystery. Suddenly Koch cast a new shaft of life, revealing to the world that he had unraveled the entire mystery of its etiology.

Then, in 1883, he followed up this discovery with another that was almost equally influential. In 1883, he isolated theVibrio cholerae. Koch then had discovered and demonstrated the role of pathogens, the ones responsible for two of the most prevalent and feared nineteenth century diseases. This marked, as I said, the definitive triumph of contagionism. And the 1880s and '90s were a golden age of microbiology, with the pathogens being discovered for a whole range of other diseases. This was an extraordinary period in medical science. The pathogens were discovered for gonorrhea, bubonic plague, dysentery, tetanus, the common bacteria of wound infections, staph infections and others. The paradox, of course, there were still few benefits for patients, until the turn of the new century.

Chapter 6. Therapeutic Effects [00:39:31]

The quip was made that the main beneficiaries, at first, of the germ theory of disease, were physicians rather than patients. But there was a major exception, and that was not in medicine but in surgery. And this introduces the third major figure of our trio, establishing the germ theory of disease, and that's Joseph Lister, who lived from 1827 to 1912, and made his major contributions in Scotland. He was professor of surgery at Edinburgh University, where he was appalled by the numbers of patients who died after otherwise successful operations. You know the old joke about the operation being successful, just too bad the patient died. Well, Pasteur's idea immediately struck him for its lifesaving, practical implications. That is, he made practical use of Pasteur's discovery about the role of airborne germs in causing wound infections in surgery.

Now, surgery, before Lister, had a number of major limits. There was pain itself, and the need for speed. There was blood loss, and there was septicemia. The result was that the major body cavities remained off limits: the abdominal cavity, the thoracic cavity, the cranial cavity. And there was a high rate of death from infection. The idea was thought by physicians at the time that the infection arose through spontaneous generation. As tissue died, they gave off toxins that caused infection, and so infection was simply accepted as an inevitable, normal part of surgery. Lister's surgical revolution occurred with the work he published, "On the Antiseptic Principle in the Practice of Surgery," in 1864.

The implications of Pasteur's work on fermentation were that — you could have an analogy. If Pasteur was right, there was no spontaneous generation. An airborne microorganism penetrated the wound and caused infection or septicemia. The remedy was to prevent the penetration of the microorganism, the idea of antisepsis. So, Lister accepted Pasteur's insight that infections were not a chemical reaction, caused by oxidation when air touched a wound. Instead, infection was the result of contamination, from the outside, of the wound by microorganisms. His solution first was this, the carbolic spray device that he invented. What you did was to spray the air around the patient, applying carbolic acid also directly to the wound. And Lister also washed his hands before operating, and sterilized his instruments. There's a stylized idea of a Lister-type surgical technique at work.

Well, until Lister's revolutionary innovation, surgery had been an emergency, a treatment of last resort, because of the wound infection. After 1866, it became a normal procedure. There were other innovations as well, that went with it. His contemporaries improved on Lister. You'll see that here they aren't wearing masks, for example, or gowns. Those are introduced — and gloves made from vulcanized rubber — were introduced in the 1890s, but really became a part of best practice only from about the time of the First World War. This also revolutionalized obstetrics, with the conquest of puerperal fever, with — hospital and clinical procedures then were transformed by the antiseptic idea. So, by the 1890s, you have the consolidation of the germ theory of disease, revolutionalizing medicine and become accepted throughout the international medical profession.

I'd like to mention the impact also on culture. And this particular book, which is by Bram Stoker, which is Dracula, published in 1897, that gives us, I would argue, expression in a really dramatic and — I just read it again — a really scary — I assure you — idea of anxieties about infection. Now, Dracula is really, for its time, a high-tech novel. In it you see all about the latest scientific and medical inventions and ideas. It contains the phonograph, the telephone, stenography, railroads, the two-wheeled bicycle. And in medicine it deals with the latest inventions in psychiatry, in blood transfusion, infectious diseases. And indeed, I would argue, it also involves what was the cutting edge scientific idea in medicine at the time, the possibility of vector borne diseases like malaria and filarial.

Then it's just at the time when we're going to see tropical medicine — we'll look at next time — becomes the cutting edge of late nineteenth-century, early twentieth-century medical science. Now, you know the drill about Dracula, how Count Dracula — the word Dracula comes from the Romanian word dracul, which means a devil, a little devil. And you know how he lived, the Count — the evil Count — in Transylvania, in Romania, in the Carpathian Mountains. And the important point is he travels by ship from the Black Sea port, aboard a Russian vehicle, through the Mediterranean, and up along the coast of Spain and France, where he lands by ship in Britain at the port of Whitby. Then he travels by train, and is transported by railroad from Whitby to London, where his plan is to ravage the huge population of London.

Now, what does that remind you of? Doesn't that — it reminds me — I'm going to argue that Dracula is many things. In literature, you'll see that Dracula is a metaphor — and this is often said — for repressed sexuality, in the Victorian Era. You'll find interpretations of it as expressing also a repressed homoeroticism. In it, we also find expression of the battle of good and evil. That's our friend Dracula. And you'll see — love never dies — the idea of — the sexual idea is clearly — some 200 films have been made of Dracula. And you can see clearly possible sexual ideas in films such as this. And they're clearly also here. But what I want to argue is what's been neglected so often — and I think it's really important — is I want to argue that Dracula is also an allegory of infectious disease; not a specific disease, but diseases like plague and cholera, that originated in Eastern Europe and traveled, just as Dracula did, by ship and by railroad; that they had Count Dracula's goal of ravaging industrial cities, huge population centers like London.

And it's interesting that the vampire hunters in the novel are doctors, physicians, whose mission is to destroy the invading vampire. Also involved, we see, is the seasonality. It's not by chance that Count Dracula arrives in late August/September, just as cholera would have, or bubonic plague. And we see miasmatism in the novel: the flowers, the garlic, the mists surrounding Dracula. And I would argue that Dracula is a composite of many infections. Here's the handsome count again. And I'd like to show you one more handsome picture of him; and that's that one. And I would argue that this clearly makes me think also of vector-borne disease, and possibly this is a million miles removed from malaria and filarial, which we'll be talking about next week. So, I urge you also to read Dracula. I'm sure you'll enjoy it as much as I did.

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