Exploring Viruses: Impact and Insights

On this episode of Assignment Discovery, travel from the rainforest to the laboratory in search of the simplest life forms on earth and meet people who are committed to understanding viruses. Find out how these tiny assassins live, reproduce, and wreak havoc on species. like our own. Then see how scientists propose to defend humanity from future epidemics. This easy to use guide will help you tape copyright cleared programs for classroom use. And turn to the internet for support or resources at Discovery Channel School Online. Make Discovery Networks work for you. Call 1-800-321-1832 or find us on the World Wide Web at school.discovery.com. Coming up now, study and discussion questions for Understanding Viruses, Part 1. How do viruses reproduce? How did World War I contribute to the influenza pandemic of 1918? Compare and contrast the work of Edward Jenner and that of Jonas Salk. How can the triumphs of these two virologists set an example for modern scientists researching new threats? Assignment Discovery now presents Understanding Viruses, Part 1. This team of army medics is rehearsing. Not for the outbreak of war, but the outbreak of virus. It's a battle where shaking hands can be more lethal than dodging bullets. Where the adversary numbers in the billions. Where nothing is constant but the body count. Viruses are things on the very edge of life. We can't taste them, smell them, or see them. But they're there. In the air, in the water, in every living thing on the planet. They're the tiniest, simplest form of life on Earth. Yet they know ways to enter our bodies, kidnap our cells, outwit our immune defenses. Viruses are old. Some believe they're older than all other forms of life. And they are patient. Without a living cell to invade, they wait in a crystalline form somewhere between life and death. Some can wait for centuries. Their only goal is to reproduce. Viruses are pure purpose. Viruses, when they're out there in the environment, are basically just pieces of genetic information wrapped up in a protein coat or some other little bit of protection, vulnerable to all the elements in general, and just waiting for the next living thing that they can grow in to come along so that they can infect and propagate themselves. It's the form of life that cannot subsist. It doesn't have the machinery with which to live. It can only do so by entering and utilizing another cell for that purpose. And when it uses human cells for that purpose, we usually end up the losers. Diseases caused by viruses are as potent a force in the history of man as war and natural... Disasters. Influenza. 15th century Italians called it that because they believed it was caused by the influence of stars and planets. Smallpox was first reported in Chinese literature 3,000 years ago, now extinct. There are seven different kinds of herpes. Chickenpox is one. Odds are you have herpes right now. Kuru is found only in cannibal tribes in New Guinea, transmitted by eating human brains. Each cold you get may feel the same, but it's not. There are hundreds of different cold viruses. In your lifetime, at least 50 of them will catch you. And the list goes on. As common as colds, as deadly as AIDS. Viruses are a cause of a lot of misery. There's the viruses you catch in the office, the daycare center, that your kids bring home from school that cause minor disease. We don't diagnose viruses specifically so that we can we often pass them off and we don't pay the kind of attention to them that we might. Viruses have always been difficult to pin down. Even the most powerful optical microscopes could only magnify objects 2,000 times. They revealed a watery world of bacteria and single-celled creatures. Eating, moving, multiplying. What they couldn't see was the phantom that destroyed cells with stunning efficiency. Then, in the 1930s, German scientists invented the electron microscope and could finally see a virus. at 7,000 times magnification. Instead of bouncing clumsy light waves off objects, it used tiny electrons to magnify. One look through the electron microscope instantly changed how people defined the boundaries of life. They discovered organisms so small, billions and billions of them could fit into a single pixel on your television screen. Scanned by electrons, viruses were revealed to be spheres and spindles and geometric shapes. They looked too symmetrical to be alive. On today's supercomputer screens, viruses look like ornaments from a Martian Christmas tree. This is the AIDS virus. Its core contains the genetic information necessary for the virus to duplicate itself. It's a package of nucleic acid, of genetic material, enveloped... In a set of proteins that allow this virus to utilize a cell for its own replication, because it cannot function independently, it cannot multiply independently. The genes are protected by a thin shell. The shell is studded with molecules that enable it to dock with the target cell and work its way inside. There are certain receptor mechanisms that come together. They attach. They don't attack, they attach, they're incorporated, and they use the cellular mechanism for its own multiplication. It acts as a parasite. It uses these organized systems for its own survival. The target cell doesn't have to be human or even animal. The tulip break virus has been used since the 16th century to cause color variation in ornamental tulips. Nothing is too small for a virus. So, naturalists observe a flea. Have smaller fleas that don't impregnate. And these have smaller fleas to bite them. And so proceed at infinitum. Yup, even germs can get germs. An example? The T4 bacteriophage, a virus that attacks bacteria. It lands, hooks on, and pushes its DNA through the cell membrane. Once inside, the viral DNA hijacks the cell and forces it to make more viruses. Within minutes, the swollen cell explodes, releasing hundreds of new viruses to infect other cells. In ancient times, people didn't know about viruses, but they did know this. Getting sick was the last thing most of them ever did. Where did these diseases come from? Was it the wrath of the gods? Omens? Sorcery? The great red plague that struck during the Peloponnesian Wars in the 5th century BC may have been typhus or scarlet fever, or it could have been measles. Smallpox was the scourge of the Middle Ages, killing many and leaving survivors permanently disfigured. When 20th century archaeologists opened Egyptian tombs, They found references to what could have been polio. But diseases of the past were limited in time and space. The world had not yet experienced viral epidemics on a global scale. One of the worst natural disasters in recorded history was caused by a virus. The influenza pandemic of 1918 struck every major US city, dropping people where they stood. There were at least 20 billion people killed worldwide. And it's probably the worst pandemic the world has ever known. There were more people killed from influenza than there were from the First World War. The war itself was the problem. If there had been no war, that year's strain would have stayed isolated. But when Allied troops met in northern France to exchange fire with the enemy, they also exchanged a lethal strain of flu. So it began. It then went from France to the United States and disseminated from Boston. At Fort Devens, Massachusetts, one case of flu turned into more than 6,000 cases between September 1st and September 18th. It took only 17 days. India lost nearly 4% of its population. Alaska, 8%. In the South Seas, the death rate was 20%. People were absolutely panicked because somebody could be playing bridge one night and they would be dead the next day. And so they did all kinds of things. They were wearing... wearing face masks and in fact the police all wore face masks. They were carrying little pouches of garlic and onion, just anything that they thought would protect them from the flu. They had no idea that they were leaving exposed the very place where flu enters the body, their noses. Nothing was known about how to cope with it. And that is something that began to emerge when we got into the 1930s, 1940s, and 1950s. By that time, there was enough knowledge and experience and the development of techniques to make it possible to proceed. Never before in history have doctors been able to do so much to preserve your health as they can today. And almost everywhere in medicine, the parade of advances that will benefit countless millions has just begun. Vaccines became a scientist's dream. They promised to rid the world of viral disease. Curiously, the word vaccine comes from a cow disease called vaccinia. In the 18th century, the beauty of milkmaids was a cliché. They alone seemed to be spared from smallpox. An English country doctor named Edward Jenner observed that a surprising number of milkmaids caught a mild, measles-like illness called cowpox, known officially as vaccinia. Jenner extracted the virus from blisters and infected a child, his own infant son. Then... He inoculated the boy with live smallpox virus. It was shockingly risky. But it worked. The initial cowpox injection did cause mild sickness, but it was enough like smallpox that his body eventually built an immunity to both diseases. We have evolved our own defense mechanisms over the years. We know this is the immune system, which is a very complex system containing many different kinds of cells and functions whose major purpose, by and large, is to recognize what's foreign and attempt to rub it out. The immune system has three major functions, which are working in your body right now, at this very second. Antibodies are proteins that bind to the surface of a virus, flagging it for death. The body's white cells move in to destroy virus-infected cells. Once you have been infected with a virus, memory cells will immediately recognize it if it enters your body again. This is why vaccines are so effective. The body remembers what the fake virus looks like, so it can protect you when the real virus comes along. One of the most common ways to make a vaccine is to grow it in an unnatural host. Chicken embryos are used to grow human viruses like yellow fever, measles, mumps, and influenza. Influenza has been grown in eggs for many, many years. It's our standard way of producing virus. It can also be grown in tissue culture and grows very well in tissue culture, but you can't produce enough tissue culture to make large doses required for industrial use. Every year, flu virus is injected into eggs. After several transfers from egg to egg, the virus will have become better adapted to growing in chicken cells than human cells. When injected into a human, it looks enough like the enemy to cause immunity, but isn't strong enough to cause sickness. The flu virus has found a way around the immune system by mutating, changing the way it looks. Sometimes it changes only slightly. Other years, the change is radical and we are defenseless. Sometimes you can get partial immunity, which will give you some protection. But when we have what we call a shift, that is usually what occurs when we have major epidemics. Then the immune system doesn't recognize the flu at all. It bears no resemblance to anything the antibodies have seen before. How much a virus can change depends on how it's made. If it has genetic material arranged in the familiar double helix DNA, then it's pretty stable from generation to generation. In reproduction, when a DNA strand unzips to become two DNA strands, a kind of molecular spelling checker watches the new molecules form to make sure the two copies are identical. The DNA viruses have a nice copy editing system so they will correct their own errors, which means that the frequency of mutation is low. The RNA viruses do not have those. And this explains why RNA viruses are so variable. These viruses change all the time. Which is why the vaccine for a DNA virus like smallpox works decade after decade, while every year we need a new vaccine for RNA viruses like influenza. This frozen library is Dr. Herlocker's collection of flu strains that have evolved over the years. These viruses are not dead, just dormant. Each vial represents a different year, a different strain. If you warmed up and breathed flu vintage 1980, you'd probably get sick. Some vintages of flu are spontaneous mutations. Other epidemics can be traced back to ducks and pigs. They end up with names like swine flu or the Hong Kong flu or the Asian flu. because they often come from countries where people live close to their farm animals. Influenza has the added advantage of crossing from one species to the next. Each time this happens, the strain changes. And that means a lot of work for scientists at the World Health Organization and Centers for Disease Control in Atlanta. Every year, it's a race against time. CDC Influenza Surveillance Laboratory. Information is gathered from flu watch centers around the world and used to predict what new strain is coming our way. Once this is determined, a new vaccine is developed, hopefully in time. It's hard for us to imagine a world without vaccines for diseases like influenza, smallpox, or polio. In the first half of this century, people panicked when children came down with fever and muscle aches. It might lead to nothing. It might end up with the child spending the rest of his days in a pressurized cylinder everyone called the iron lung. In my own lifetime, I was aware of the effect of viruses. In 1916, for example, which was two years after I was born, there was this severe polio epidemic in the United States, particularly in New York City. And then again in 1918-1919 there was a severe influenza epidemic. And in both instances the effect was quite devastating. Now I of course was too young to understand the significance of that, but I do remember. The crippled bodies and the coffins. Nobody knew why polio caused polio. paralysis or death, much less that it could be transmitted in contaminated food, water, or spittle. Home remedies and preventatives were born out of desperation. When polio struck Franklin Roosevelt after he had gone swimming, he was in a state of shock. in a chilly lake, people speculated that the cold water must have been the cause. By the late 1940s, a young Jonas Salk was well on his way to becoming a hero to parents worldwide. My whole life has been devoted to being a physician, and this is the way in which I chose to practice medicine. And so this is what the pattern of my life has been, to try to... to either prevent disease or heal or cure in some way. His breakthrough came when Harvard scientists found a way to grow poliovirus in quantity. Salk had the raw material he needed to develop a vaccine. My whole approach to this, that one could immunize against a virus disease without experiencing infection. Until then, it was believed that you had to experience infection, as against smallpox. rabies, an attenuated form of the virus. In his lab at the University of Pittsburgh, Salk killed poliovirus with formaldehyde to prevent it from causing disease. In 1955, after first trying it on himself, he began inoculating children. The dead virus alerted their immune systems without making them sick. It was treated as the biggest news in medical history. In the United States alone, two generations have grown up without knowing the anguish of the disease. It was all in a day's work, I like to say. And it was appreciated, especially by your parents, for whom fear was lifted. Back in 1935, a bacteriologist called the battle against disease one of the last genuine adventures in the world. The dragons are all dead, and the lance grows rusty in the chimney corner. sporting proposition that remains is the war against those ferocious little fellow creatures which lurk in the dark corners and stalk us in the bodies of rats which fly and crawl with the insects and waylay us in our food and drink and even in our love. Coming up now, answers to the questions for Understanding Viruses, Part 1. Viruses are unable to reproduce on their own, so they insert their genetic information into other cells that can reproduce for them. During World War I, people from many countries came into close contact. This allowed one strain of influenza to spread around the world at an unprecedented rate. Try this activity with your class. Have each student draw and label a diagram of an animal cell and a virus. Then make a list of all the similarities and differences between the two. Why is a virus considered to exist between life and death? To learn more, members of the American Association of School Librarians and Assignment Discovery suggest Viruses by Howard and Marjorie Faclum. Ask your librarian to help you explore the many resources your library has to offer. Coming up now, study and discussion questions for Understanding Viruses, Part 2. Why is it important for virologists to study life forms in tropical rainforests? How might viruses be used to cure some genetic diseases? Discuss the two examples in the documentary where disease was used as a weapon. What are some of the potential consequences of using viruses in this manner? Assignment Discovery now presents Understanding Viruses, Part 2. Today, new crusaders struggle to slay the littlest dragons that lurk in the world of poverty. The rotavirus, a tiny waterborne microbe that kills over 5 million children a year. 5 million, mainly in countries of the developing world. In the war against Drodovirus, this is the battlefield, a village in central Brazil. The town is called Terra Firma, but it's built precariously over the Guana River. The Guana River is the only running water here. It's the local sewage system. Unfortunately, it's also the local water supply. In collaboration with the World Health Organization, Dr. Alexander Linares and his team from the Instituto Evandro Chagas in Brazil track the rotavirus and try to help young mothers battle the disease. Boiled water is hard to come by. Sanitation is hard in a floating slum in the tropics. The virus is so stable that human-to-human transmission perpetuates. in the community. We know that improving sanitation conditions, improving hygiene is very important, but it's not sufficient in order to control rotavirus diarrhea. It is necessary to have an effective vaccine. The researchers monitor the children's health and test their blood to study how they develop antibodies to the virus. They conduct field trials evaluating the efficiency of a candidate vaccine. This vaccine, if approved, could potentially save 800,000 young lives a year. It would require mass immunization, but that's an area where the World Health Organization already has a lot of experience. In 1967, they decided to kill a disease, smallpox. We have never driven any infection to extinction. Smallpox was the very first time that finally the world got together and decided. that if we were going to cause species to go extinct, let's do it for a good purpose, for a change. International teams of doctors and nurses were sent door to door tracing the last case of smallpox to Somalia. It's absolutely amazing to see the way they did it. They had groups, teams of doctors and nurses go all around the world in the deserts, in the Sierras, and all around the world. Every country in the world, they vaccinated everybody. The smallpox virus can only grow in human beings. Vaccinations kept it from spreading to new hosts, so when the last victim recovered, the chain of transmission was broken forever. Smallpox, the disease, disappeared from the earth in 1978. Smallpox, the virus, is still around. These stark hallways lead to what may be its final resting place. Only two collections are left in the world, and they are kept in Moscow and here at the Centers for Disease Control in Atlanta. The World Health Organization wants them destroyed, but not everyone agrees. We didn't want to totally eliminate the virus box because we didn't... understand the virus and what made it tick. It's part of the whole basic fundamental argument about diversity, biological diversity. Can we afford to lose these organisms that have established themselves in a particular The greater danger is the possibility of smallpox accidentally escaping from a freezer somewhere, where there might be a forgotten stock stored, or years from now after people have forgotten about it. The whole idea of smallpox escaping and decimating unimmunized populations may seem like science fiction, but it happened hundreds of years ago. In 1519, Hernando Cortes invaded Mexico and conquered millions of Aztecs. He did it with less than 600 men, a few horses, some primitive guns, and, with a weapon he didn't know he had, a virus unknown in the New World. The Aztecs and their immune systems were defenseless. What was often attributed to the will of God was actually the work of man. This time the transmission of the virus may not have been so innocent. According to some experts, Lord Geoffrey Amherst of Massachusetts Bay Colony ordered the distribution of smallpox-infected blankets among local Indian tribes. The age of exploration became a perfect vehicle for viruses. Today, it's no different, just more efficient. Global commerce. Overpopulation. Teeming cities. Progress. But progress is not without its price. We continue to create highways for what scientists now call viral emergence, a steady stream of old viruses getting out to look for new hosts. As people introduce themselves into environments that used to be inaccessible to human habitation and to human exploration, suddenly these viruses spring out. And they spring out at us because we're putting ourselves there and we're putting ourselves in their path. And so in many cases these viruses that seem to come out of nowhere really do come from somewhere. They come from nature. They're just like all other life forms. They've been there and what's new is the opportunities we have given them without realizing it to meet new people. Among the planet's remaining natural environments, few are changing faster than the tropical rainforests. Experts estimate that 90% of the 14 million species on the earth are unknown to us. And all of those unknown plants and animals can harbor unknown viruses. That's what we face when we're in the middle of a pandemic. when we destroy the rainforest. I think we're going to see emergence of more disease, and I think everybody would agree we need people out there who are familiar with the diseases in local areas, who can describe the trends in diseases, and who will see a new disease when it comes along. Everybody's got the fever, that is something you all know. Senor Helio Augusto Cardoso Cereva is part of a team of physicians and scientists trying to predict the pathways of viral emergence. His job? Bait. Augusto is bug bait. He waits patiently in the canopy of the Brazilian rainforest for mosquitoes to bite him. Augusto and his colleagues are part of an early warning system for arboviruses. Arboviruses are carried by insects that live in the treetops and on the forest floor. Bugs come to a sudden end as they and their cargo of viruses are frozen in liquid nitrogen for the 10 mile trip to the Evandro Chagas Institute in Belém, Brazil. In the lab, researchers thaw the insects and sort them under a microscope. These mosquitoes may be dead, but their viruses will be intact, waiting for the appropriate conditions to spring back to life. In a phase of the project that gives rich new meaning to the term the daily grind, the bugs are smashed into a liquid. That green mosquito soup is then injected into lab mice. Some will develop problems with locomotion. Some will die within hours. Some will develop infections of the scariest viruses known, diseases like yellow fever. The Institute has isolated 30 strains of virus that cause disease in humans. From mosquitoes alone, the Institute has found 40 viral strains the world never knew before. Insects are not the only way viruses travel. During the Korean War, thousands of GIs were felled by a strange fever. Later named after Korea's Hantan River, Hantavirus caused hemorrhaging, kidney failure, and death. It was eventually traced back to the urine of field mice who lived in rice paddies. A similar illness appeared suddenly in the southwest United States in 1993. Disease detectives from the Centers for Disease Control quickly targeted the Hantavirus group. They, too, traced it back to mice. Once we had the rodent reservoir, then we had an opportunity to try to plan specific strategies so that people could avoid those particular kinds of rodents. Avoiding the rodents is all we can do. At this point, we are still vulnerable to hantaviruses. There is no effective treatment, and outbreaks are virtually impossible to predict. Steve Abrams, David Lange... Nothing shows our vulnerability more starkly than AIDS, the disease caused by HIV. It is a virus whose relentless march around the globe continues to shape the history of this century. Robert Michael McCabe... No one has pinpointed HIV's origin. At the Salk Institute in Southern California, Dr. Salk has turned his attention to AIDS. He accepts the idea that it was a mutation of a monkey virus that first appeared centuries ago. It moved into the human population. very likely as a result of the ritual use of monkey blood. And then it remained at a low level of frequency, probably in villages where it was contained. And then, as civilization began to expand and travel, ...became possible not only in airplanes but in trucks and other forms of transportation and people moved about they simply spread it. HIV, human immunodeficiency virus, is one of a fast mutating RNA family. This HIV virus, which is really very small, not only will go into the immune system and kill the immune system, but it doesn't do it immediately. It can remain latent for a long period of time. It uses this property of retroviruses to make a DNA copy of itself which will go into the host. integrate there and why it can remain silent. And then a cure cell cannot do anything, just sees the cell, it's a nice cell, cannot see that inside there is the invader, the invader is hidden. So the fact that the virus can be hidden makes it extremely difficult to fight. The search for ways to cure AIDS brings researchers together from all over the world. They report on everything from funding to the health of prostitutes in the poorest slums of Nairobi. Discussions focus on why some people who have been exposed to HIV don't have AIDS. These women may represent the first known cases of natural immunity to HIV. Following that evidence of an experiment in nature, which is very much like what is being observed in Kenya, it begins to suggest to us what would be the strategy that should be used. in developing a vaccine. If we can begin to understand the nature of the relationship and how it functions, then we can develop strategies to cope with it. And the fact that there's clear evidence in humans that there is such a thing as a successful interaction with HIV is all that we need to know. That tells us it's possible. Nature is telling us something. At Fort Detrick, Maryland, an Army Special Forces medical team is on 24-hour alert. If a soldier gets a disease that's deadly, infectious, unidentified, or all three, these medics are on the first C-141 out of Andrews Air Force Base. With typical military precision, they call themselves USAMRID. Located on an army base 45 miles from Washington DC. Working out of a facility best known for biological warfare research, the team could be on the front lines of the military. line in the war against emerging viruses. They are prepared to face some of the worst diseases in the world, like Ebola or green monkey fever. Relatively new and incredibly deadly, Ebola was first identified in the Sudanese and Zaire in 1976. By 1989 it threatened to infect a community just 70 miles from USAMRID. Fortunately it was just a threat but that's not always the case. A person unlucky enough to contract some exotic disease, known or not, could quickly find himself on his way to Maryland. Ready? Everybody ready? Ready. One, two, three. It would be a strange trip, with the patient watching the action first from inside an isolation stretcher, then from an airtight capsule aboard a cargo plane. The virus, the victim, and the medics would be off to the sealed hospital rooms at the institute. Pressurized spacesuits may make them look like miniature parade balloons, but if the suit should spring a leak, air would rush out instead of in. The medics pass through disinfectant showers to a room where the air is carefully filtered, where wastes travel through cement-encased sewer lines to be sterilized. Once the patient is in place in the hot suite, the hard work can start. In a different type of hospital room, viruses are actually being used to help rather than hurt. I think it would be wonderful poetic justice to think that viruses are enemies, could be used to help cure genetic diseases. I think in the future we can expect to see... more and more of viruses being used in gene therapy and obviously intentionally as vectors for introducing new genes. Researchers are in the beginning stages of using a virus's ability to break into a cell to change inborn defects in the genetic code. Experiments are underway to deliver a gene missing in people with cystic fibrosis. In this case, the part of a cold virus that makes you sick is deleted and replaced with the gene needed to cure cystic fibrosis. Then, it's set free to do what cold viruses do. It targets the cells of the respiratory tract. But instead of taking over the cell for its own purposes, it delivers the missing DNA. So the relationship between viruses and humans continues to evolve. Just as they have always used us, we are now using them. Regardless of who is in control, mankind's tiniest foe is not going away. I think if a virus comes along with a broad enough host range, that we could suffer a real serious depredation in the number of people in our species. I think you have to consider that as a real possibility. I don't want to be a doom. prophesy or say what's going to happen tomorrow or so on, but I think that HIV should have run the wake-up call. HIV, the AIDS pandemic, I think should be a lesson to all of us and it's sad that we have to pay such a heavy price to relearn a lesson we've known for many years that the infectious diseases will never disappear we can push them to the margins of our existence we can try to control them by and large we can learn to live with them but we have to learn to deal with them and we have to deal with them we can't just ignore them viruses are part of nature can we not accept the fact that they're part of nature and so are we It's all here. If you want an exclusive right, we're going to have to accept viruses. They're not going to go away. So we stand locked in mortal combat with the humblest of Earth's creatures. And the best we can hope for is a truce. The alternative is that humankind, pleased to consider itself the pinnacle of creation, could fall victim to some drifting bits of genetic material straddling the line between life and death. Coming up now, answers to the questions for Understanding Viruses, Part 2. By studying life forms in tropical rainforests, virologists will start to understand viruses that may someday infect humans. Viruses can be loaded with genes capable of curing a defect in human cells. When the altered virus is released into the body, it can target and take over the defective cells. Try this activity with your class. Find an article about the eradication of smallpox in 1978 and write a letter to the editor in response to it. Focus your letter on the ethics of eradicating life forms that threaten the human population. To learn more, members of the American Association of School Librarians and Assignment Discovery suggest Viruses by Peter Jarrett. Ask your librarian to help you explore the many resources your library has to offer.

Then see how scientists propose to defend humanity from future epidemics. This easy to use guide will help you tape copyright cleared programs for classroom use. And turn to the internet for support or resources at Discovery Channel School Online. Make Discovery Networks work for you.

Call 1-800-321-1832 or find us on the World Wide Web at school.discovery.com. Coming up now, study and discussion questions for Understanding Viruses, Part 1. How do viruses reproduce? How did World War I contribute to the influenza pandemic of 1918? Compare and contrast the work of Edward Jenner and that of Jonas Salk. How can the triumphs of these two virologists set an example for modern scientists researching new threats?

Assignment Discovery now presents Understanding Viruses, Part 1. This team of army medics is rehearsing. Not for the outbreak of war, but the outbreak of virus. It's a battle where shaking hands can be more lethal than dodging bullets.

Where the adversary numbers in the billions. Where nothing is constant but the body count. Viruses are things on the very edge of life.

We can't taste them, smell them, or see them. But they're there. In the air, in the water, in every living thing on the planet.

They're the tiniest, simplest form of life on Earth. Yet they know ways to enter our bodies, kidnap our cells, outwit our immune defenses. Viruses are old.

Some believe they're older than all other forms of life. And they are patient. Without a living cell to invade, they wait in a crystalline form somewhere between life and death.

Some can wait for centuries. Their only goal is to reproduce. Viruses are pure purpose.

Viruses, when they're out there in the environment, are basically just pieces of genetic information wrapped up in a protein coat or some other little bit of protection, vulnerable to all the elements in general, and just waiting for the next living thing that they can grow in to come along so that they can infect and propagate themselves. It's the form of life that cannot subsist. It doesn't have the machinery with which to live.

It can only do so by entering and utilizing another cell for that purpose. And when it uses human cells for that purpose, we usually end up the losers. Diseases caused by viruses are as potent a force in the history of man as war and natural...

Disasters. Influenza. 15th century Italians called it that because they believed it was caused by the influence of stars and planets.

Smallpox was first reported in Chinese literature 3,000 years ago, now extinct. There are seven different kinds of herpes. Chickenpox is one. Odds are you have herpes right now.

Kuru is found only in cannibal tribes in New Guinea, transmitted by eating human brains. Each cold you get may feel the same, but it's not. There are hundreds of different cold viruses. In your lifetime, at least 50 of them will catch you. And the list goes on.

As common as colds, as deadly as AIDS. Viruses are a cause of a lot of misery. There's the viruses you catch in the office, the daycare center, that your kids bring home from school that cause minor disease.

We don't diagnose viruses specifically so that we can we often pass them off and we don't pay the kind of attention to them that we might. Viruses have always been difficult to pin down. Even the most powerful optical microscopes could only magnify objects 2,000 times.

They revealed a watery world of bacteria and single-celled creatures. Eating, moving, multiplying. What they couldn't see was the phantom that destroyed cells with stunning efficiency. Then, in the 1930s, German scientists invented the electron microscope and could finally see a virus.

at 7,000 times magnification. Instead of bouncing clumsy light waves off objects, it used tiny electrons to magnify. One look through the electron microscope instantly changed how people defined the boundaries of life.

They discovered organisms so small, billions and billions of them could fit into a single pixel on your television screen. Scanned by electrons, viruses were revealed to be spheres and spindles and geometric shapes. They looked too symmetrical to be alive.

On today's supercomputer screens, viruses look like ornaments from a Martian Christmas tree. This is the AIDS virus. Its core contains the genetic information necessary for the virus to duplicate itself.

It's a package of nucleic acid, of genetic material, enveloped... In a set of proteins that allow this virus to utilize a cell for its own replication, because it cannot function independently, it cannot multiply independently. The genes are protected by a thin shell. The shell is studded with molecules that enable it to dock with the target cell and work its way inside.

There are certain receptor mechanisms that come together. They attach. They don't attack, they attach, they're incorporated, and they use the cellular mechanism for its own multiplication. It acts as a parasite. It uses these organized systems for its own survival.

The target cell doesn't have to be human or even animal. The tulip break virus has been used since the 16th century to cause color variation in ornamental tulips. Nothing is too small for a virus. So, naturalists observe a flea. Have smaller fleas that don't impregnate.

And these have smaller fleas to bite them. And so proceed at infinitum. Yup, even germs can get germs.

An example? The T4 bacteriophage, a virus that attacks bacteria. It lands, hooks on, and pushes its DNA through the cell membrane.

Once inside, the viral DNA hijacks the cell and forces it to make more viruses. Within minutes, the swollen cell explodes, releasing hundreds of new viruses to infect other cells. In ancient times, people didn't know about viruses, but they did know this.

Getting sick was the last thing most of them ever did. Where did these diseases come from? Was it the wrath of the gods?

Omens? Sorcery? The great red plague that struck during the Peloponnesian Wars in the 5th century BC may have been typhus or scarlet fever, or it could have been measles.

Smallpox was the scourge of the Middle Ages, killing many and leaving survivors permanently disfigured. When 20th century archaeologists opened Egyptian tombs, They found references to what could have been polio. But diseases of the past were limited in time and space.

The world had not yet experienced viral epidemics on a global scale. One of the worst natural disasters in recorded history was caused by a virus. The influenza pandemic of 1918 struck every major US city, dropping people where they stood.

There were at least 20 billion people killed worldwide. And it's probably the worst pandemic the world has ever known. There were more people killed from influenza than there were from the First World War. The war itself was the problem.

If there had been no war, that year's strain would have stayed isolated. But when Allied troops met in northern France to exchange fire with the enemy, they also exchanged a lethal strain of flu. So it began.

It then went from France to the United States and disseminated from Boston. At Fort Devens, Massachusetts, one case of flu turned into more than 6,000 cases between September 1st and September 18th. It took only 17 days. India lost nearly 4% of its population.

Alaska, 8%. In the South Seas, the death rate was 20%. People were absolutely panicked because somebody could be playing bridge one night and they would be dead the next day. And so they did all kinds of things. They were wearing...

wearing face masks and in fact the police all wore face masks. They were carrying little pouches of garlic and onion, just anything that they thought would protect them from the flu. They had no idea that they were leaving exposed the very place where flu enters the body, their noses.

Nothing was known about how to cope with it. And that is something that began to emerge when we got into the 1930s, 1940s, and 1950s. By that time, there was enough knowledge and experience and the development of techniques to make it possible to proceed.

Never before in history have doctors been able to do so much to preserve your health as they can today. And almost everywhere in medicine, the parade of advances that will benefit countless millions has just begun. Vaccines became a scientist's dream.

They promised to rid the world of viral disease. Curiously, the word vaccine comes from a cow disease called vaccinia. In the 18th century, the beauty of milkmaids was a cliché.

They alone seemed to be spared from smallpox. An English country doctor named Edward Jenner observed that a surprising number of milkmaids caught a mild, measles-like illness called cowpox, known officially as vaccinia. Jenner extracted the virus from blisters and infected a child, his own infant son. Then...

He inoculated the boy with live smallpox virus. It was shockingly risky. But it worked. The initial cowpox injection did cause mild sickness, but it was enough like smallpox that his body eventually built an immunity to both diseases. We have evolved our own defense mechanisms over the years.

We know this is the immune system, which is a very complex system containing many different kinds of cells and functions whose major purpose, by and large, is to recognize what's foreign and attempt to rub it out. The immune system has three major functions, which are working in your body right now, at this very second. Antibodies are proteins that bind to the surface of a virus, flagging it for death.

The body's white cells move in to destroy virus-infected cells. Once you have been infected with a virus, memory cells will immediately recognize it if it enters your body again. This is why vaccines are so effective.

The body remembers what the fake virus looks like, so it can protect you when the real virus comes along. One of the most common ways to make a vaccine is to grow it in an unnatural host. Chicken embryos are used to grow human viruses like yellow fever, measles, mumps, and influenza.

Influenza has been grown in eggs for many, many years. It's our standard way of producing virus. It can also be grown in tissue culture and grows very well in tissue culture, but you can't produce enough tissue culture to make large doses required for industrial use.

Every year, flu virus is injected into eggs. After several transfers from egg to egg, the virus will have become better adapted to growing in chicken cells than human cells. When injected into a human, it looks enough like the enemy to cause immunity, but isn't strong enough to cause sickness.

The flu virus has found a way around the immune system by mutating, changing the way it looks. Sometimes it changes only slightly. Other years, the change is radical and we are defenseless.

Sometimes you can get partial immunity, which will give you some protection. But when we have what we call a shift, that is usually what occurs when we have major epidemics. Then the immune system doesn't recognize the flu at all.

It bears no resemblance to anything the antibodies have seen before. How much a virus can change depends on how it's made. If it has genetic material arranged in the familiar double helix DNA, then it's pretty stable from generation to generation. In reproduction, when a DNA strand unzips to become two DNA strands, a kind of molecular spelling checker watches the new molecules form to make sure the two copies are identical.

The DNA viruses have a nice copy editing system so they will correct their own errors, which means that the frequency of mutation is low. The RNA viruses do not have those. And this explains why RNA viruses are so variable.

These viruses change all the time. Which is why the vaccine for a DNA virus like smallpox works decade after decade, while every year we need a new vaccine for RNA viruses like influenza. This frozen library is Dr. Herlocker's collection of flu strains that have evolved over the years. These viruses are not dead, just dormant.

Each vial represents a different year, a different strain. If you warmed up and breathed flu vintage 1980, you'd probably get sick. Some vintages of flu are spontaneous mutations.

Other epidemics can be traced back to ducks and pigs. They end up with names like swine flu or the Hong Kong flu or the Asian flu. because they often come from countries where people live close to their farm animals.

Influenza has the added advantage of crossing from one species to the next. Each time this happens, the strain changes. And that means a lot of work for scientists at the World Health Organization and Centers for Disease Control in Atlanta. Every year, it's a race against time. CDC Influenza Surveillance Laboratory.

Information is gathered from flu watch centers around the world and used to predict what new strain is coming our way. Once this is determined, a new vaccine is developed, hopefully in time. It's hard for us to imagine a world without vaccines for diseases like influenza, smallpox, or polio. In the first half of this century, people panicked when children came down with fever and muscle aches. It might lead to nothing.

It might end up with the child spending the rest of his days in a pressurized cylinder everyone called the iron lung. In my own lifetime, I was aware of the effect of viruses. In 1916, for example, which was two years after I was born, there was this severe polio epidemic in the United States, particularly in New York City. And then again in 1918-1919 there was a severe influenza epidemic.

And in both instances the effect was quite devastating. Now I of course was too young to understand the significance of that, but I do remember. The crippled bodies and the coffins. Nobody knew why polio caused polio. paralysis or death, much less that it could be transmitted in contaminated food, water, or spittle.

Home remedies and preventatives were born out of desperation. When polio struck Franklin Roosevelt after he had gone swimming, he was in a state of shock. in a chilly lake, people speculated that the cold water must have been the cause. By the late 1940s, a young Jonas Salk was well on his way to becoming a hero to parents worldwide. My whole life has been devoted to being a physician, and this is the way in which I chose to practice medicine.

And so this is what the pattern of my life has been, to try to... to either prevent disease or heal or cure in some way. His breakthrough came when Harvard scientists found a way to grow poliovirus in quantity. Salk had the raw material he needed to develop a vaccine.

My whole approach to this, that one could immunize against a virus disease without experiencing infection. Until then, it was believed that you had to experience infection, as against smallpox. rabies, an attenuated form of the virus.

In his lab at the University of Pittsburgh, Salk killed poliovirus with formaldehyde to prevent it from causing disease. In 1955, after first trying it on himself, he began inoculating children. The dead virus alerted their immune systems without making them sick.

It was treated as the biggest news in medical history. In the United States alone, two generations have grown up without knowing the anguish of the disease. It was all in a day's work, I like to say.

And it was appreciated, especially by your parents, for whom fear was lifted. Back in 1935, a bacteriologist called the battle against disease one of the last genuine adventures in the world. The dragons are all dead, and the lance grows rusty in the chimney corner. sporting proposition that remains is the war against those ferocious little fellow creatures which lurk in the dark corners and stalk us in the bodies of rats which fly and crawl with the insects and waylay us in our food and drink and even in our love.

Coming up now, answers to the questions for Understanding Viruses, Part 1. Viruses are unable to reproduce on their own, so they insert their genetic information into other cells that can reproduce for them. During World War I, people from many countries came into close contact. This allowed one strain of influenza to spread around the world at an unprecedented rate.

Try this activity with your class. Have each student draw and label a diagram of an animal cell and a virus. Then make a list of all the similarities and differences between the two. Why is a virus considered to exist between life and death? To learn more, members of the American Association of School Librarians and Assignment Discovery suggest Viruses by Howard and Marjorie Faclum.

Ask your librarian to help you explore the many resources your library has to offer. Coming up now, study and discussion questions for Understanding Viruses, Part 2. Why is it important for virologists to study life forms in tropical rainforests? How might viruses be used to cure some genetic diseases?

Discuss the two examples in the documentary where disease was used as a weapon. What are some of the potential consequences of using viruses in this manner? Assignment Discovery now presents Understanding Viruses, Part 2. Today, new crusaders struggle to slay the littlest dragons that lurk in the world of poverty. The rotavirus, a tiny waterborne microbe that kills over 5 million children a year.

5 million, mainly in countries of the developing world. In the war against Drodovirus, this is the battlefield, a village in central Brazil. The town is called Terra Firma, but it's built precariously over the Guana River.

The Guana River is the only running water here. It's the local sewage system. Unfortunately, it's also the local water supply. In collaboration with the World Health Organization, Dr. Alexander Linares and his team from the Instituto Evandro Chagas in Brazil track the rotavirus and try to help young mothers battle the disease.

Boiled water is hard to come by. Sanitation is hard in a floating slum in the tropics. The virus is so stable that human-to-human transmission perpetuates. in the community. We know that improving sanitation conditions, improving hygiene is very important, but it's not sufficient in order to control rotavirus diarrhea.

It is necessary to have an effective vaccine. The researchers monitor the children's health and test their blood to study how they develop antibodies to the virus. They conduct field trials evaluating the efficiency of a candidate vaccine. This vaccine, if approved, could potentially save 800,000 young lives a year. It would require mass immunization, but that's an area where the World Health Organization already has a lot of experience.

In 1967, they decided to kill a disease, smallpox. We have never driven any infection to extinction. Smallpox was the very first time that finally the world got together and decided.

that if we were going to cause species to go extinct, let's do it for a good purpose, for a change. International teams of doctors and nurses were sent door to door tracing the last case of smallpox to Somalia. It's absolutely amazing to see the way they did it.

They had groups, teams of doctors and nurses go all around the world in the deserts, in the Sierras, and all around the world. Every country in the world, they vaccinated everybody. The smallpox virus can only grow in human beings.

Vaccinations kept it from spreading to new hosts, so when the last victim recovered, the chain of transmission was broken forever. Smallpox, the disease, disappeared from the earth in 1978. Smallpox, the virus, is still around. These stark hallways lead to what may be its final resting place.

Only two collections are left in the world, and they are kept in Moscow and here at the Centers for Disease Control in Atlanta. The World Health Organization wants them destroyed, but not everyone agrees. We didn't want to totally eliminate the virus box because we didn't... understand the virus and what made it tick. It's part of the whole basic fundamental argument about diversity, biological diversity.

Can we afford to lose these organisms that have established themselves in a particular The greater danger is the possibility of smallpox accidentally escaping from a freezer somewhere, where there might be a forgotten stock stored, or years from now after people have forgotten about it. The whole idea of smallpox escaping and decimating unimmunized populations may seem like science fiction, but it happened hundreds of years ago. In 1519, Hernando Cortes invaded Mexico and conquered millions of Aztecs. He did it with less than 600 men, a few horses, some primitive guns, and, with a weapon he didn't know he had, a virus unknown in the New World. The Aztecs and their immune systems were defenseless.

What was often attributed to the will of God was actually the work of man. This time the transmission of the virus may not have been so innocent. According to some experts, Lord Geoffrey Amherst of Massachusetts Bay Colony ordered the distribution of smallpox-infected blankets among local Indian tribes.

The age of exploration became a perfect vehicle for viruses. Today, it's no different, just more efficient. Global commerce. Overpopulation.

Teeming cities. Progress. But progress is not without its price.

We continue to create highways for what scientists now call viral emergence, a steady stream of old viruses getting out to look for new hosts. As people introduce themselves into environments that used to be inaccessible to human habitation and to human exploration, suddenly these viruses spring out. And they spring out at us because we're putting ourselves there and we're putting ourselves in their path. And so in many cases these viruses that seem to come out of nowhere really do come from somewhere.

They come from nature. They're just like all other life forms. They've been there and what's new is the opportunities we have given them without realizing it to meet new people. Among the planet's remaining natural environments, few are changing faster than the tropical rainforests.

Experts estimate that 90% of the 14 million species on the earth are unknown to us. And all of those unknown plants and animals can harbor unknown viruses. That's what we face when we're in the middle of a pandemic. when we destroy the rainforest. I think we're going to see emergence of more disease, and I think everybody would agree we need people out there who are familiar with the diseases in local areas, who can describe the trends in diseases, and who will see a new disease when it comes along.

Everybody's got the fever, that is something you all know. Senor Helio Augusto Cardoso Cereva is part of a team of physicians and scientists trying to predict the pathways of viral emergence. His job? Bait.

Augusto is bug bait. He waits patiently in the canopy of the Brazilian rainforest for mosquitoes to bite him. Augusto and his colleagues are part of an early warning system for arboviruses. Arboviruses are carried by insects that live in the treetops and on the forest floor.

Bugs come to a sudden end as they and their cargo of viruses are frozen in liquid nitrogen for the 10 mile trip to the Evandro Chagas Institute in Belém, Brazil. In the lab, researchers thaw the insects and sort them under a microscope. These mosquitoes may be dead, but their viruses will be intact, waiting for the appropriate conditions to spring back to life.

In a phase of the project that gives rich new meaning to the term the daily grind, the bugs are smashed into a liquid. That green mosquito soup is then injected into lab mice. Some will develop problems with locomotion. Some will die within hours.

Some will develop infections of the scariest viruses known, diseases like yellow fever. The Institute has isolated 30 strains of virus that cause disease in humans. From mosquitoes alone, the Institute has found 40 viral strains the world never knew before. Insects are not the only way viruses travel.

During the Korean War, thousands of GIs were felled by a strange fever. Later named after Korea's Hantan River, Hantavirus caused hemorrhaging, kidney failure, and death. It was eventually traced back to the urine of field mice who lived in rice paddies.

A similar illness appeared suddenly in the southwest United States in 1993. Disease detectives from the Centers for Disease Control quickly targeted the Hantavirus group. They, too, traced it back to mice. Once we had the rodent reservoir, then we had an opportunity to try to plan specific strategies so that people could avoid those particular kinds of rodents. Avoiding the rodents is all we can do. At this point, we are still vulnerable to hantaviruses.

There is no effective treatment, and outbreaks are virtually impossible to predict. Steve Abrams, David Lange... Nothing shows our vulnerability more starkly than AIDS, the disease caused by HIV.

It is a virus whose relentless march around the globe continues to shape the history of this century. Robert Michael McCabe... No one has pinpointed HIV's origin.

At the Salk Institute in Southern California, Dr. Salk has turned his attention to AIDS. He accepts the idea that it was a mutation of a monkey virus that first appeared centuries ago. It moved into the human population.

very likely as a result of the ritual use of monkey blood. And then it remained at a low level of frequency, probably in villages where it was contained. And then, as civilization began to expand and travel, ...became possible not only in airplanes but in trucks and other forms of transportation and people moved about they simply spread it.

HIV, human immunodeficiency virus, is one of a fast mutating RNA family. This HIV virus, which is really very small, not only will go into the immune system and kill the immune system, but it doesn't do it immediately. It can remain latent for a long period of time. It uses this property of retroviruses to make a DNA copy of itself which will go into the host.

integrate there and why it can remain silent. And then a cure cell cannot do anything, just sees the cell, it's a nice cell, cannot see that inside there is the invader, the invader is hidden. So the fact that the virus can be hidden makes it extremely difficult to fight.

The search for ways to cure AIDS brings researchers together from all over the world. They report on everything from funding to the health of prostitutes in the poorest slums of Nairobi. Discussions focus on why some people who have been exposed to HIV don't have AIDS.

These women may represent the first known cases of natural immunity to HIV. Following that evidence of an experiment in nature, which is very much like what is being observed in Kenya, it begins to suggest to us what would be the strategy that should be used. in developing a vaccine. If we can begin to understand the nature of the relationship and how it functions, then we can develop strategies to cope with it. And the fact that there's clear evidence in humans that there is such a thing as a successful interaction with HIV is all that we need to know.

That tells us it's possible. Nature is telling us something. At Fort Detrick, Maryland, an Army Special Forces medical team is on 24-hour alert. If a soldier gets a disease that's deadly, infectious, unidentified, or all three, these medics are on the first C-141 out of Andrews Air Force Base. With typical military precision, they call themselves USAMRID.

Located on an army base 45 miles from Washington DC. Working out of a facility best known for biological warfare research, the team could be on the front lines of the military. line in the war against emerging viruses. They are prepared to face some of the worst diseases in the world, like Ebola or green monkey fever. Relatively new and incredibly deadly, Ebola was first identified in the Sudanese and Zaire in 1976. By 1989 it threatened to infect a community just 70 miles from USAMRID.

Fortunately it was just a threat but that's not always the case. A person unlucky enough to contract some exotic disease, known or not, could quickly find himself on his way to Maryland. Ready? Everybody ready? Ready.

One, two, three. It would be a strange trip, with the patient watching the action first from inside an isolation stretcher, then from an airtight capsule aboard a cargo plane. The virus, the victim, and the medics would be off to the sealed hospital rooms at the institute.

Pressurized spacesuits may make them look like miniature parade balloons, but if the suit should spring a leak, air would rush out instead of in. The medics pass through disinfectant showers to a room where the air is carefully filtered, where wastes travel through cement-encased sewer lines to be sterilized. Once the patient is in place in the hot suite, the hard work can start.

In a different type of hospital room, viruses are actually being used to help rather than hurt. I think it would be wonderful poetic justice to think that viruses are enemies, could be used to help cure genetic diseases. I think in the future we can expect to see...

more and more of viruses being used in gene therapy and obviously intentionally as vectors for introducing new genes. Researchers are in the beginning stages of using a virus's ability to break into a cell to change inborn defects in the genetic code. Experiments are underway to deliver a gene missing in people with cystic fibrosis.

In this case, the part of a cold virus that makes you sick is deleted and replaced with the gene needed to cure cystic fibrosis. Then, it's set free to do what cold viruses do. It targets the cells of the respiratory tract.

But instead of taking over the cell for its own purposes, it delivers the missing DNA. So the relationship between viruses and humans continues to evolve. Just as they have always used us, we are now using them. Regardless of who is in control, mankind's tiniest foe is not going away. I think if a virus comes along with a broad enough host range, that we could suffer a real serious depredation in the number of people in our species.

I think you have to consider that as a real possibility. I don't want to be a doom. prophesy or say what's going to happen tomorrow or so on, but I think that HIV should have run the wake-up call. HIV, the AIDS pandemic, I think should be a lesson to all of us and it's sad that we have to pay such a heavy price to relearn a lesson we've known for many years that the infectious diseases will never disappear we can push them to the margins of our existence we can try to control them by and large we can learn to live with them but we have to learn to deal with them and we have to deal with them we can't just ignore them viruses are part of nature can we not accept the fact that they're part of nature and so are we It's all here. If you want an exclusive right, we're going to have to accept viruses.

They're not going to go away. So we stand locked in mortal combat with the humblest of Earth's creatures. And the best we can hope for is a truce. The alternative is that humankind, pleased to consider itself the pinnacle of creation, could fall victim to some drifting bits of genetic material straddling the line between life and death. Coming up now, answers to the questions for Understanding Viruses, Part 2. By studying life forms in tropical rainforests, virologists will start to understand viruses that may someday infect humans.

Viruses can be loaded with genes capable of curing a defect in human cells. When the altered virus is released into the body, it can target and take over the defective cells. Try this activity with your class.

Find an article about the eradication of smallpox in 1978 and write a letter to the editor in response to it. Focus your letter on the ethics of eradicating life forms that threaten the human population. To learn more, members of the American Association of School Librarians and Assignment Discovery suggest Viruses by Peter Jarrett. Ask your librarian to help you explore the many resources your library has to offer.

Transcript for:Exploring Viruses: Impact and Insights

Transcript for:
Exploring Viruses: Impact and Insights