HIST 234: Epidemics in Western Society Since 1600

Lecture 17

 - Malaria (II): The Global Challenge


In the last decade of the nineteenth century, malariology emerged as the most prestigious and intellectually exciting field in the new discipline of tropical medicine. The disease’s complexity and resistance to conventional public health strategies posed a major challenge to doctors and scientists. Plague measures and social hygiene had no effect in curbing malaria, and the disease proved difficult to classify. The case of Italy, and the malaria eradication program of 1900-1962, furnished a model for other efforts across the world. In evaluating the Italian campaign, it is important to distinguish between valuable lessons and warnings for future efforts, and in particular to account for the diversity of strategies responsible for its success.

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Epidemics in Western Society Since 1600

HIST 234 - Lecture 17 - Malaria (II): The Global Challenge

Chapter 1. The Complexity of Malaria [00:00:00]

Professor Frank Snowden: What I want to do this morning is first of all begin by recapitulating a couple of points that we made last time. You’ll recognize our friend here, having her blood feast, and last time we talked about the importance of malaria in human history for a little bit, from ancient times to the contemporary world, and we tried to suggest that malaria continues to impose an extraordinary burden of suffering and death, along with those consequences that follow in its train: poverty, low productivity, illiteracy, a low level of political, social and education participation.

We also talked, as you’ll remember, about the transmission of the disease, with the complex lifecycle of plasmodia andAnopheles mosquitoes. We talked about the effect of the disease on the human body of the patient and symptoms that result from malaria, and we tried to deal also with the great years of discovery at the end of the 1890s, between 1898 and 1901, when the great mysteries of this disease were largely unraveled in two different places. First in India, with the collaboration of Ronald Ross and Patrick Manson, they demonstrated the mosquito transmission of malaria with regard to avian malaria — that is, among birds. And then the other place, even more importantly, was Italy, where Giovanni Battista Grassi and other scientists of what was called the Italian School, or the Rome School, proved the mosquito theory of transmission for human beings.

I hope that in that discussion, it was apparent to all of you that malaria is by far the most complex of all the diseases that we’ve studied, or will study, in our course. And that point is important and underlies the fact that we spent a lot of time talking about the complexity of the disease. It’s important because it helps us to understand a great deal of the history. One point is that if we understand that, we’re in a position to understand also why research on malaria generated such intense intellectual excitement in the 1890s. It was then that malariology because the centerpiece for the new medical discipline of tropical medicine. Here was one of the world’s oldest and most important public health problems, and suddenly it was yielding its secrets.

There was a tremendous excitement intellectually, and malariology attracted some of the world’s leading scientists and public health officials. We also wanted to talk about the complexity of malaria, because a second reason is that it helps us to understand why the public health strategies that we’ve examined so far haven’t worked in dealing with malaria. If we think, for example, what are the main public health strategies that we’ve discussed so far — one was plague measures. You know the drill by now: sanitary cordons, quarantines, isolation. These, however, prove to be powerless against a disease that’s borne by vectors as efficient and mobile as Anopheles mosquitoes.

In high malarial endemicity areas, mosquitoes are infinitely numerous and infinitely mobile. Plague measures would be no help at all. We can understand also why another form of public health was useless. The sanitary movement was irrelevant. Malaria is not like cholera. It’s not a disease of filth or the bacteria that thrive in it. Places that are immaculately clean can be lethally infested with mosquitoes and the plasmodia that they bear. Furthermore, malaria is a disease of rural areas, primarily, and urban cleanups were therefore largely irrelevant in combating it. So, a second strategy of public health that we’ve confronted so far was powerless in dealing with this disease.

Another public health strategy that we’ve examined was the strategy of vaccination, and we’ve seen that pioneered by Edward Jenner, and developed much more by Louis Pasteur. And this too, thus far, has proved unavailing with regard to malaria. Let’s think for a moment about vaccines, and I’d like to argue that they’re effective primarily under certain conditions, that they aren’t universal panaceas for all diseases. They’re helpful primarily, first of all, in combating diseases against which the body develops a robust acquired immunity.

Smallpox is a perfect example. A patient who has once suffered from smallpox, but then recovers, is then immune for the rest of his or her life. And, so, the strategy for vaccination is to produce artificially the same effective immune response that was generated by the naturally occurring infection. The strategy then is to reproduce what nature does on her own. But in malaria, the immune response of the body is limited, and it takes multiple infections and recovery there from to acquire a partial immunity, and that immunity even then is short-lived. It’s partial and short-lived.

If you have painfully acquired an immunity from malaria and then you move away from the malarial area, in a couple of years your immunity fades away, and if you return to the malaria area you’re susceptible all over again. So, this is one factor that makes vaccine development so very complicated. Another point about vaccine development is that vaccines haven’t so far been developed against a pathogen with a lifecycle as complex as that of a plasmodium.

In targeting a virus or bacterium, a vaccine is always dealing quite simply with the virus or the bacterium. But the point about studying about — one of the points about investigating the lifecycle of the plasmodium is that they’re different. They go through a series of complicated life stages. Sometimes they’re sporozoites. Sometimes they’re merozoites. Sometimes they’re gametocytes. And the problem with a vaccine is that in order to be viable, it has to be effective against all of those phases in the lifecycle of the plasmodium.

And then also another feature, as I said, is that malaria is not a single disease. It’s a family of four different parasitic diseases, and the vaccine has to be effective against not simply one, but against numerous, therefore, species of parasite. Now, I don’t want to argue that therefore the development of a vaccine against malaria is impossible. In fact, as we’re speaking, scientists are hard at work trying to develop such a vaccine, and indeed, they have come up with one. You read some rather silly things in the press. The vaccine developers came up with a vaccine in the last few years that’s about thirty-percent effective.

I remember reading in places like the New York Times that malaria would therefore be eradicated globally in five to seven years. This is a sort of rather silly prediction, and even the people — I know because I’ve talked to them — who are developing the vaccine have no such illusion about its efficacy. They’re thrilled because it’s thirty-percent effective, but that means that it’s seventy-percent not effective.

Chapter 2. A Societal View of Malaria: Characterization [00:10:00]

Well, in order to understand the evolution of public health strategies against malaria and the problem facing the world today in dealing with this disease, then we need to know that the very complexity of malaria has led to a wide array of different strategies to combat it, as well as to an ongoing debate on which course is likely to be most effective. And as yet there’s no consensus in the international health community on the best and most effective strategy, despite the fact that since the turn of the twentieth century, at the least, malaria is a disease, paradoxically, that has such extraordinary ravages on the global population, and yet, paradoxically, it’s a disease that’s both treatable and preventable. There is an amazing paradox.

This morning, then, I want to talk about not the effects, the nature of the plasmodium, the nature of mosquitoes, the lifecycle or symptomatology of malaria, but I’d like to look instead at the disease from the societal point of view, and in particular on efforts to development a successful antimalarial strategy. But developing a strategy or thinking about the proper strategy against malaria is easier if we think of a number of ways in which this disease might be characterized, the ways in which it has been seen by leading scientists, physician, and public health officials who’ve dealt with it. So, I’m wondering if we could think of malaria — we might ask a number of questions about it.

How should we describe this disease? Is it a disease of poverty, and what’s the evidence for that? That would entail dealing with — and in a particular way that might be different from other ways. One of the leading world malariologists in the early twentieth century defined malaria as a house disease. In other words, it’s primarily defined by poor housing conditions in which people are crowded in order to work in agricultural occupations, and those houses are porous to insects, and it’s in the house that the disease is transmitted, and both mosquitoes and human beings are infected. Or should we see it instead as an occupational disease? We’ve talked about the relationship of malaria to agriculture, and it’s quite clear that certain forms of agricultural production create and generate high risk for those who practice them, and malaria is contracted overwhelmingly by people who work in fields under certain conditions.

Another way of thinking about it is, in that case, one way of attacking a malaria then would be to have occupation improve the conditions of farming, of agriculture, to regulate rice fields and all the rest of it. That would be what you would do, perhaps, if you define it as an occupational disease. Should we think of it instead as an environmental disease, that it’s a disease that flourishes where the environment has been degraded? Where there’s been deforestation, for example. Where the hydrology of rivers has been undermined. Where there’s flooding of places where there are swamps and impounded water. In that case, the way of dealing with malaria, you might think, might be to have land drainage, reclamation, environmental sanitation — quite a different strategy for dealing with the disease.

What should we call this particular disease? Is it an endemic disease, or is it an epidemic disease? And here I think that malaria is one of those diseases that we’re studying in our course that’s actually both. That is to say, in a particular locality, it is an endemic disease. For example, if you were to go to the tropical areas of Africa today, malaria is present throughout the year. It’s highly, even hyper endemic. But it’s also capable of being an epidemic disease. First of all, that’s easiest to see, perhaps, it temperate zones where malaria has also been prevalent, because then it’s seasonal and you have the winter when the disease — it’s too cold for the plasmodium to be transmitted, but you have an annual summer epidemic. But in addition, under certain conditions we would say that the epidemic is intensified in conditions, for example, of years of exceptionally heavy rainfall. Or, say, in tropical Africa, it becomes an epidemic disease when something happens to the environment, where there are complex emergencies or famines that cause people to move in large numbers — who lack immunity to move to areas where the disease is prevalent.

So, malaria can cause extraordinarily intense epidemics against a background of being also an endemic disease. I would like to argue, and I will be arguing that part of the complexity of malaria — and if I were asked the question — although you may want to disagree with me, because people are still arguing about how one defines a malaria and how one deals with it. But I’d like to suggest that perhaps it’s all of those. It’s a disease of poverty. This is part of its complexity, its biological, social, and environmental complexity. It is a disease of poverty. It’s also a house disease. It’s an occupational disease. It’s an environmental disease. It’s an endemic disease. And it’s an epidemic disease as well.

Chapter 3. Historical Strategies [00:17:08]

Well, what are the kinds of strategies that have been deployed against this dreadful disease? One was since we now know that it’s transmitted by vectors, Ronald Ross, who was one of the people who won the Nobel Prize, in fact for establishing that very idea, developed very question the idea then if it’s a disease that’s transmitted by vectors, perhaps the right course for dealing with malaria is vector control. Kill mosquitoes by insecticides, or remove their breeding grounds by environmental sanitation, by dealing with an unregulated hydrology of an area, by land drainage, by removing uncovered water.

A different strategy would be to deal with not the mosquito but with the plasmodium. And so there have been — and here I’ve talked about the Italian School of malariology, and Giovanni Battista Grassi had the idea that you would be able to eradicate malaria by the use of antiplasmodial — that is, quinine — one the first effective magic bullets. He thought the idea was that if we know what causes malaria and there is an effective treatment for it, if you can use it prophylactically to prevent people from being infected for a number of seasons in a particular geographical area, or if you can destroy the plasmodia in the bloodstreams of all of the sufferers, then you can prevent mosquitoes from being infected for the following year. And if you do that for several seasons, then you could break the cycle of transmission and eradicate malaria.

Both of the people who discovered the mosquito theory of transmission very quickly came to the idea of malarial eradication. Ross did so, and Grassi immediately thought that malaria had what he called — it was the “colossus with feet of clay” — and that quinine would be the instrument that would enable the world to eradicate it. But if you think of it as a disease of poverty, you might think instead — and a disease of housing, and an occupation disease — then you might think of a different strategy of social uplift, that what you need to do to deal with malaria is to practice social medicine to deal with poor diet, poor wages, child labor — those whole series of complex factors that create the substratum in which malaria thrives.

And then there is another strategy which is quite commonly thought of. It has not made much progress, at least to date, though who knows, maybe it will in the future, and that’s the Jenner/Pasteurian strategy of hoping to develop an effective antimalarial vaccine. So vaccine development is one of the great hopes in the antimalarial struggle, and enormous amounts of resources are being invested in antimalarial vaccine development as we speak. Well, I want to give an example of a particular place. It’s the one you’re reading about this week, which was the impact of malaria on a particular country. And I’ve chosen Italy for particular reasons. One is that Italy had a special relationship to malaria. It was the only Western European country where it wasn’t a colonial issue, but rather the most important domestic public health problem. It was also the international center of malariology from about 1900 until the Second World War.

In other words, we’ve talked about the hegemony of powers in international medicine in the early nineteenth century down the middle of the nineteenth century. In the smaller domain of malariology, Italy was the center of the action from 1900 until World War II. This is the place where people went to be trained in malariology. People traveled — physicians from all over the world — to study with those people who were called the Rome School, or the Italian School of malariology — Giovanni Battista Grassi most prominent. But other names were extremely prominent also, like Angelo Celli, and we could list a whole series of others. And it was Italians primarily who were responsible for unraveling the mysteries of malaria.

Chapter 4. Italian Eradication [00:23:14]

And finally, Italy was a place that did something quite extraordinary. It was the first place to have a successful strategy of antimalarial campaigning. In other words, a campaign began in 1900 and was successful in a eradicating malaria by 1962. The last indigenous case of malaria in Italy was in Sicily in 1962. So, this means that Italy has lessons, and there are not many places where there have been campaigns that have succeeded intentionally in eradicating the disease. This leads to a message of hope — what can be accomplished by doing it, and it also means that I think it’s useful to look at the this successful campaign in order to draw lessons from it, but to beware also of the misuse of history, because a lot of what I think are the wrong lessons have also been drawn from it.

Well, in any case, let’s look just very, very quickly at the Italian experience. As you know, Italy was united in the middle of the nineteenth century, and by the 1880s the new liberal regime became aware of the prevalence of the disease throughout the country, and this is the map that was — it’s not the best map artistically or even in terms of clarity, or I would even say in terms of accuracy; and, so, you’re wondering why do I show you this map of malaria in Italy when there are actually better maps that are more colorful and all the rest? But for historians, this is the important one, because this is the one that shook Italians up and convinced them of the enormity of the problem in their country.

One of the things that’s quite clear, even in looking at this map, is that malaria was present everywhere virtually. There are areas that are yellow, pink, and red of prominence or extreme prominence of malaria. And it was the case also that after unification, instead of the problem — unification seen as a foundational moment for this new regime that’s supposed to deliver civilization, economic betterment, progress, and also public health — but instead, the years at the end of the nineteenth century see the malarial problem, already intense, getting worse. Worse because of things like deforestation of the Apennines.

The railroad era actually had a devastating impact, because it led to the demand for trees to make the railroad ties and the stations and all the rest, and therefore led to massive deforestation and deregulation of the hydrology of the entire peninsula, which was turned topsy-turvy. It was also a time then of economic difficulties and crises, and malaria feeds on human misfortune, and it did so in the late nineteenth century. Well, in any case, Italy also provided — we’ve talked about malaria as a housing disease — I thought I’d just show you a representative type of peasant housing, even down through the 1930s and ’40s, and when you live in places like this, in a malarial area, you’re highly vulnerable because this is almost like being outdoors. In fact, it’s probably worse in terms of mosquitoes. It’s entirely vulnerable and open to flying insects, and having numerous people sleeping in conditions like this helps to promote the disease and transmission.

Similarly, we talked about it being an occupational disease. It wasn’t by chance that Italy is also a place of rice fields, and rice fields are actually wonderful places for mosquitoes, and the rice workers were among those people who were most vulnerable, and became symbolic as the victims of the plasmodia. So, in any case then, there was an epidemic and endemic condition in Italy. And Italy showed all of those terrible consequences of malaria that we’ve been talking about: absenteeism in agriculture; waste — whole areas that weren’t cultivated because they were so dangerous, and those who did work on them sickened and died; an area of low productivity, of illiteracy; the underdevelopment of civil society; low participation in politics; mass emigration.

And I would argue indeed that one of the features of Italy is that we’ve talked about North and South, and I talked about agriculture being a determinant of malaria, and that the global North had advanced forms of agriculture that were intensive and not conducive to malaria; and the South, the global South, had the opposite. Well, this was reproduced in a microcosm in Italy in that the North of Italy was much less vulnerable to malaria, and the form of malaria was the mildervivax malaria, while the South of Italy was riddled with malaria, and it was malaria that predominantly falciparum; that is, the most devastating and lethal form of the disease.

Well, there was a time of great scientific discoveries that we’ve talked about. Oh, this is a famous picture, just to show you. This is a painting called “Malaria,” and as you see, it’s sort of like a pietà , or a deposition from the cross, and I think it conveys, in a moving, emotional way, the reaction of a society to intense malarial transmission. This is the prime minister at the turn of the century until the First World War, under whom the antimalarial campaign gets started. And this is Giovanni Battista Grassi — I tried to show him last time — who was the person who proves the mosquito transmission among human beings, the leading representative of the Rome School of malariology, and his work was — we’ve talked about institutions — this is the Santo Spirito Hospital, where he conducted his research, because there were an enormous, almost unending supply, of malarial patients. And it was here that he first successfully infected human beings with malaria with a number of scientific experiments, that you might consider ethically problematic, but in any case, there weren’t rules about such things at the turn of the twentieth century.

Well, the pillars of the eradication program — the pillar of it was initially going to be quinine. And so Italy passed a series of quinine laws from 1900 to 1907, with support from the liberal prime minister. And the idea was that you could kill the plasmodia, break the cycle of transmission, and eradicate the disease. Grassi thought it would be merely a matter of a few years. In fact, it then turned out to be impossible to eradicate the disease so easily that people were not used to contact with physicians. There wasn’t access, in other words, to medical care. Distributing quinine was tremendously problematic. It also has to be followed according to a very complex regimen, and it has to be followed for months at a time, and you can’t get people to do that unless they understand the disease.

And, so, actually to have an effective antimalarial program, turned out you have also to deal with poverty and with illiteracy, which are the allies of the mosquito and of malaria. And so it was important to teach people the discipline of quinine and the reasons for it so very quickly, and also health access was important. And, so, new parts of the program turned out to be rural health stations. It’s expanding now beyond quinine to include rural health stations, education and rural schools. In other words, a whole panoply of things that we might call social medicine, improved housing. Actually, Celli argues that trade unions were a powerful antimalarial tool because they helped deliver better wages, and with that, better diet and better clothing, and child labor laws — and we know that children are particularly susceptible to malaria — and the regulation of occupations that were particularly dangerous, such as working in rice fields.

Well, the results of the liberal program, which has expanded well beyond distributing quinine — in other words, it starts with the vision of a magic bullet and moves very quickly to a whole panoply of things that we might, for shorthand, call social uplift, with having to do with access to medical care, improved housing, civil liberties, education, and all of those sorts of measures. The results of the liberal program, by the eve of the First World War, were a massive decline in mortality, at least, but still the persistence of the disease. And then comes World War I, which was an extraordinary setback for malaria. And I’ve talked about the way that malaria is a disease that thrives on human misfortune, and there is no misfortune that is better for malaria than war.

I thought I would show you a few paintings of the First World War to show you the kinds of conditions that led in Italy that destroyed, almost, the first fifteen, sixteen years of antimalarial efforts, and created this huge explosion of epidemic malaria during the First World War. And this is a famous painter — Sartorio is his name — who was a combatant in the First World War, but then was wounded, and returned to the front as a painter — rather, as a photographer — and he took photographs of the conditions at the fighting front, and then he did paintings from his photographs. And these are some of the most impressive, I think, moving pictures of the sorts of conditions. You can see exactly how mosquitoes would thrive in conditions of this sort. This is not dead soldiers. These are soldiers bivouacking after a battle, and I think you can imagine them being from non-malarial areas and not having resistance, and you can see that they are a wonderful feast for Anopheles mosquitoes, and the soldiers from non-malarial areas fell sick and died in enormous measures.

We’ve talked about malaria as a housing disease. Well, also the destruction of housing renders people vulnerable; if you have to move into tents or into the open fields to bivouac, to move from area to area, from cities to the rural areas and all the rest of it, you become extraordinarily vulnerable. And, so, the destruction of housing and the housing stock was extremely important. So, there was this tremendous upsurge of malaria during the First World War. After the First World War, in 1922, we have a new regime, and this was the fascist regime of Benito Mussolini. We won’t talk about the conditions that brought Mussolini to power, but we now have a totalitarian, one-party dictatorship — the end of elections, police repression, violence, the secret police, and a foreign policy of expansion to restore an empire and to pursue broad European and African conquest.

By the end of the 1920s, Mussolini is fully in power, and he institutes some antimalarial measures that became extremely famous, and he’s often thought as a hero of the antimalarial movement because of what he did in this area — the Pontine Marshes — which is just outside of Rome, and you’ll be reading about that. This was done, however, for political purposes more than for medical ones, because the point about the Pontine Marshes was that only a couple of thousand people lived there in 1930, and this became the height of the regime’s antimalarial measures, which were to drain the swamps, to build new housing, and to settle the land. But it doesn’t actually confront malaria in the parts of Italy where the most numerous people were getting ill and dying. It was an enormous propaganda effort to demonstrate, more than health, the power of the regime: that Mussolini could succeed where liberals had failed, where the popes had failed.

The sorts of measures that were undertaken, this is the kinds of conditions that he found — the swamp conditions. I guess I’m overdoing it, but I’m showing you there was plenty of water and there were plenty of mosquitoes, and it was estimated that you had an eighty percent chance of contracting malaria if you spent a single night in this area in the summer, before the drainage of the swamps. Well, this is the construction of something modestly called the Mussolini Canal, and we’ll see also it went pumping stations, land drainage; you see canals being constructed; water being raised to be harmlessly diverted to the sea went with it as well; the distribution of quinine — I’m showing quinine being distributed; education and literacy, and the teaching about the mosquito theory of transmission — all of that was important.

We see fascist Boy Scouts learning about larvae and their collection, and taking that information home to their families, was part of the idea. Here they’re doing the same thing. There were sanatoria. And you see the improved housing. These are sturdy houses. They have screened windows and all the rest of it. You see screens going up. So, this was really a huge, huge project. It also included things that weren’t so — the building of new cities. Suddenly an area that was a swamp, you see modern cities going up. The display of power is enormous. This was really an idea that had as much to do with the power of the regime as with public health. I’m not saying that it’s my view that fascism is in fact bad for your health rather than good for it.

Here are some of the propaganda pictures of the first peasant of Italy here, among his smiling, happy crowds, and all the rest of it. So, this was used in that way. Well then, part of fascism, however, you can’t understand it without its impetus to expansion and to war. And the Second World War, again, led to a major destruction and to devastation, repeating even a worse scale what had happened during the First World War. So, I won’t talk about that. I won’t talk either this morning about a war crime that I do discuss in the book, that will see the use of malaria as an instrument of bioterrorism.

Chapter 5. Eradication After World War II [00:41:29]

But my theme this morning is what are the tools for dealing with malaria, and the lessons that can be learned.

And, so, I’d like to look then — with the downfall of fascism and another terrible upsurge of malaria during the Second World War, there is a campaign to eradicate malaria that gets underway 1945-1946, and succeeds by 1962. And it’s done with Allied cooperation, the leadership of the Rockefeller Foundation and money from this country, and it involves the idea of a powerful new weapon to destroy mosquitoes — a technological weapon. DDT was discovered during the war and is now used as an instrument, a powerful insecticide, to destroy malaria. And this is thought, in fact, to be — and becomes — a premise, if we like. The lesson is drawn that malaria was eradicated in Italy after the use of DDT, and so DDT is thought to be the cause of the destruction of malaria, the successful campaign. And this becomes the premise for an international campaign, a global campaign, of the World Health Organization from 1955 until 1969 to use DDT worldwide to eradicate malaria globally.

I want to argue that this is in fact misleading, because the wrong lessons were drawn from what happened in Italy. In actual fact, the eradication after World War II was possible in part because it marked not only the use of DDT, but it also meant a massive investment of American aid to provide food, clothing, housing and employment, that becomes, first, UNRA, and then the Marshall Aid Plan. And so there is an enormous campaign to improve housing and conditions of people. In other words, there’s a massive social uplift, if we like, that’s going along at the same time as the use of DDT. At the same time, you have the reestablishment of healthcare services and rural health stations, and the massive distribution of quinine and artificial quinines developed during the war — Atabrine and chloroquine.

So, it’s not a simple, unidimensional program that succeeds. By 1962, Italy becomes malaria-free, and I think that’s one of the factors that led to the possibility of the economic miracle, and Italy’s becoming after, by our day, the world’s seventh industrial power. So, there’s an amazing measure of hope of what can be done. When you eradicate malaria, you unleash productivity and development. But in addition, this example then becomes the basis of the post World War II program of global eradication that believed that it would be possible simply to have a panacea, a technological intervention with DDT, and this is an experiment that by 1969 collapses in failure, and I would like to argue that this ought to lead us to enormous questions about today’s antimalarial program of the World Health Organization, Roll Back Malaria, and very often it’s thought that the development of using some sort of magic bullet would be adequate.

I want to argue that this was partly based on a misunderstanding of the Italian lesson, and I think we’re dealing with, in our own world, the consequences of that in the form, now, of either DDT- or insecticide-treated bed nets as being the most useful instruments; and I think the campaign is having enormous difficulties, and I think we need to think about how we define this disease — what is its substratum; what conditions promote it; and what kinds of strategies are effective in combating it. So, thank you.

[end of transcript]

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