Dr. D.A. Henderson | Smallpox: The Death of a Disease

October 30, 2009

Dr. Kent: Welcome back to Sound Authors. My next guest on the show is Dr. D.A. Henderson. He’s the author of ‘Smallpox: Death of a Disease.’ This book is an account of challenges, obstacles and disasters faced by an intrepid international program in achieving the global eradication of smallpox. Fascinating, fascinating tale. Welcome to the show, Dr. D.A. Henderson.

Dr. D.A. Henderson: Delighted to be with you.

Dr. Kent: Give me a little background about it. What is smallpox?

Dr. D.A. Henderson: Smallpox was probably the most devastating disease known to history. It goes back at least 3500 years, and has caused tens of millions of deaths, hundreds of millions of deaths, over the century. It’s a virus disease: it causes a severe rash, a high fever. The person who acquires it has about a 30 percent chance of dying from the disease, and some of those who recover are left blind. Throughout history, it was regarded as probably the most feared out of all the diseases: it’s worse than cholera or yellow fever, or any of the other diseases.

Dr. Kent: My goodness. How was it part of Americans’ lives early this century?

Dr. D.A. Henderson: It certainly kept going throughout the US until 1949; that was when our last cases occurred. One of the remarkable things is that the American Indians, the natives here in this country and throughout the western hemisphere, were particularly susceptible to it. So death rates of 60 to 80 percent were recorded. In fact, they recorded the fact that so many people died, that they couldn’t harvest the food to keep going, and whole tribes disappeared.

Dr. Kent: Wow. The toll just during the 20th century, according to your bio, says that there were 300 to 500 million deaths.

Dr. D.A. Henderson: That’s a fairly conservative estimate. Before the disease was eradicated (the last case occurred in 1977), we estimated that there were at least 300 million deaths. One compares that to what the New York Times has said how many people died as a result directly or indirectly of our conflicts in the 20th century, they estimate about 120 million, so it was more than two and half times that number dying as a result of smallpox in various countries throughout the world.

Dr. Kent: There’s such a hubbub around vaccines these days. Celebrities are starting not to vaccinate their children. This buzz is starting. With a father who’s a physician, he always tells me it’s foolish not to vaccinate, and part of the reason is because there’s such power in vaccines, and of course, with smallpox, my goodness, of course 500 million deaths, that’s a huge number that can be prevented by a vaccine. So tell me about the vaccine: how it works, how you started to think about coming up with it, or how the whole community did.

Dr. D.A. Henderson: The smallpox vaccine is actually largely comprised of another virus called cowpox, which did infect cows. It’s sort of a cousin of smallpox. It started very early that they found they could inoculate this material into the arm, and there would be an infection: a little pustule would form. The individual would then develop protective antibodies, antibodies in the blood, so that when the individual is exposed to smallpox, the antibodies would fight off the infection. This is the way vaccines work. Some of them, what they call ‘kill’ vaccines, you take a virus, like influenza, and you grow up a certain quantity of it, and you kill that virus and actually you inoculate it into the skin, and that really is your vaccine. Your body makes protective antibodies against that virus, which is dead – it’s growing – and when you are then exposed to the live virus, those antibodies are fighting off the invasion of the live virus.

Dr. Kent: Wow. How do you eradicate, even using something as incredible as this vaccination, how do you eradicate a disease? How can you get every single case?

Dr. D.A. Henderson: In fact, we did not try to get every single case. What we tried to do was provide a vaccine protection to let’s say 80 percent of the population. Now smallpox cannot infect animals, and it cannot just lie in the soil and infect people. So therefore, that virus, to keep going, it has to infect one person after another. One after the other. Think of it as a chain of infection. Now if we can stop that virus from infecting one person, and one person from infecting another, we then can break that chain and gradually get rid of the disease. So what we did was try to first of all protect a lot of people, by vaccination, and then we did something that’s called surveillance and containment: basically, find the cases. Once you’ve found a case, a team would go out and they’d vaccinate, in Africa for example, 30 houses around where the case was, all of the people there. Those people would then be protected. Then the patient could not spread the disease to anybody else. The chain would be broken, and little by little, you’d stop the spread of smallpox throughout the area.

Dr. Kent: Fascinating. Is that a technique that has been used before?

Dr. D.A. Henderson: Yes, it actually goes back a long time. Our first vaccine, the smallpox vaccine, goes back to 1796, and this was the discovery that you could take cowpox, or a little infection off of a cow and protect an individual person with that. So it had been used off and on, although it had been used pretty much on, until the time of eradication. But it was impossible really to get that vaccine out to distant areas, so that it wasn’t destroyed by feat, then to get it properly inserted in the skin so that it would really grow, and to do this throughout a lot of parts of the world which are very remote, and which are virtually inaccessible. So, it left places, areas and people where the smallpox could keep going and did keep going.

Dr. Kent: Wow. What other diseases could potentially be eradicated completely? There’s so many out there in the world, is it possible to eliminate some of these, and are efforts going on?

Dr. D.A. Henderson: It’s pretty hard to get rid of a lot of diseases. A number of them, like tuberculosis, an individual gets infected, and they get perhaps temporarily cured, but they’re still carrying the organism and can still transmit it. Poliomyelitis, for example, the individual spreads the disease, but you can’t tell where it is, because only one person in about 200 will get paralyzed, and the others will be infected, but there will be no symptoms, so that makes it difficult. There are some organisms that really largely exist in animals, and so we only get in contact with them periodically, like rabies: people know about that in dogs, and man does not get infected very often. So there are a lot of diseases that we cannot eradicate. Smallpox, fortunately, having been the most disastrous of all the diseases, had this weakness that it did not infect animals, and individuals, when they recovered from the disease, if they did, they were protected: they’d never get another case for the rest of their lives. So this was what we took advantage of with smallpox, and then tried to eradicate it.

Dr. Kent: Smallpox was essentially destroyed, but you talk about that there are stockpiles of this disease in certain places, and that could potentially be used as a weapon.

Dr. D.A. Henderson: It’s a worry. We do know that back in the ’70s, ’80s, ’90s, that the Soviet Union was working with smallpox. It was the preferred agent that they would use if they were going to use a biological weapon. So, this was a concern. When we got our last case, which actually occurred October 26, 1977, we then wrote to laboratories, contacted people all over the world who might still have some virus of smallpox. They were asked to destroy these; governments were asked to check their laboratories and to destroy them, or to transfer them to one of two laboratories which had been research laboratories that were working with us: one being actually in Moscow, one being in Atlanta, Georgia. After a while, all of the laboratories insisted finally that they had destroyed the virus or transferred it. It left us just the two places that we knew had the smallpox virus. Since then, there’s been continuing discussion as to whether those should be destroyed or not. This has been studied by many experts and scientists. I think most believe that it would be a good idea, let’s just destroy it. There’s some who believe that we might be able to learn something by retaining it, keeping it, and working with it, but there’s always a risk in that. The question is: are you going to risk having it escape, for example, or are you going to destroy it? This is something that is being discussed in the World Health Assembly and the World Health Organization: trying to reach a decision on this.

Dr. Kent: Well, it’s been such an honor talking to Dr. D.A. Henderson. He’s the author of ‘Smallpox: Death of a Disease.’ It’s so riveting thinking about all of this. I appreciate you being on the show, and I hope to talk to you again.

Dr. D.A. Henderson: Thank you very much; nice to be with you.

Dr. Kent: Again, you can find that book all over the place. It’s called, ‘Smallpox: Death of a Disease,’ by Dr. D.A. Henderson.

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