Surviving Ebola

PBS Airdate: October 8, 2014

NARRATOR: It's 10 a.m. at the Centers for Disease Control, in Atlanta, Georgia.

DR. INGER DAMON (Centers for Disease Control and Prevention): It has again been a busy week, and there's going to be a lot of issues that we need to address today. So, some of the priority issues are going to be thinking about staffing for Senegal.

US OFFICIAL: We look forward to deploying more staff next week.

INGER DAMON: Chief science officer?

CHIEF SCIENCE OFFICER: …started to tackle the issue of mutation, potential mutation of the virus.

NARRATOR: At the daily briefing, American officials are tracking the spread of the deadly Ebola virus.

AMERICAN OFFICIAL: Yeah, the outbreak is bad, and it's getting worse.

NARRATOR: This is the worst Ebola epidemic there's ever been.

AMERICAN OFFICIAL: …a couple of weeks ago has surpassed all previously recorded cases of Ebola.

NARRATOR: And people are still getting sick.

INGER DAMON: We hope that we will win, but I think we have a lot of work ahead of us.

NARRATOR: But there is hope.

WALTER ODONG: You have heard about the outbreak in West Africa. If we succeed we would be able to control, kind of, such situations.

WILL POOLEY (Volunteer Nurse): I feel so lucky to be alive. And there are a lot of people dying, elsewhere, that are not as fortunate as me.

NARRATOR: NOVA meets health workers on the frontline, encountering unimaginable tragedy,…

COKIE VAN DER VELDE (Medecins Sans Frontières): Luckily, in a protective suit, no one can see if you're crying, so no one can tell.

SANDRA SMILEY (Medecins Sans Frontières): People are very fearful of health care workers, and I can understand. Can you imagine? They take one of your loved ones away, only to return the loved one in a body bag?

NARRATOR: …and follows the scientists racing to find a cure for one of the most dangerous killers on Earth.

PROFESSOR CHARLES ARNTZEN (Biodesign Institute, Arizona State University): To scale this up to make a thousand doses or 5,000 doses, that's like trying to get a little hybrid to compete with a Maserati.

NARRATOR: This is an extraordinary story of bravery and determination against a deadly enemy: Surviving Ebola, right now, on NOVA.

On a Sunday night, a Royal Air Force plane flies into London from Sierra Leone, on board, a British nurse suffering from Ebola.

WILL POOLEY: There were moments in the flight when I was, I was feeling quite unwell and was afraid. My temperature went up quite quickly. It was a scary time.

DR. MICHAEL JACOBS (Royal Free Hospital): I first heard in the middle of the night and began to put the plan into operation, and by the next day, it was in full flow.

WILL POOLEY: In the ambulance, I remember I had a nurse. I remember her telling me about the police bikes doing, sort of, relays, shutting the road off as we drove along.

NARRATOR: Once in the hospital, Will Pooley was about to receive an experimental treatment called ZMapp™.

WILL POOLEY: Getting into hospital was, yeah, a great comfort to me.

NARRATOR: At this point, only a small number of people who are sick with Ebola have arrived in the U.S. and Europe. But the story of the outbreak began months ago, when fear and devastation came to West Africa.

On the 6th of December, 2013, a child much like this one, living in a remote village in Guinea, West Africa, died from a mysterious illness. The boy's symptoms included fever, black stool and vomiting. His painful death went unnoticed by the outside world, and we don't even know his name.

But to epidemiologists, the scientists who study disease, he now has an unforgettable identity: Patient Zero. His was the first suspected case of what has now become the largest outbreak of Ebola the world has ever seen.

Within weeks, the boy's mother, sister and grandmother all died, after suffering the same horrific symptoms. Then two local nurses who had treated the family also died. The epidemic had begun.

But how? Where had the Ebola virus been hiding?

Scientists aren't sure, but they think that African fruit bats may carry the virus, without being affected. Many people in Guinea handle and eat these bats and other animals caught in the wild, any of which could potentially be infected, creating a path for the virus to jump into humans.

However Patient Zero contracted the virus, it soon swept into a neighboring village, probably taken there by mourners who had attended one of the first local funerals. And then it was taken into another village, and then another and another, and so the chain of infection spread ever wider.

Because there had never been an outbreak in Guinea before, locals were slow to recognize the symptoms. It wasn't until 15 long weeks after the first deaths that the epidemic was confirmed.

At the Centers for Disease Control, in Atlanta, Dr. Inger Damon believes this delay has made the outbreak harder to contain.

INGER DAMON: There was a delay in being able to effectively recognize it and then to respond to it. And the delay in response…you see additional generations of cases develop, as people don't know what to do to protect themselves or protect their communities.

NARRATOR: By late March, as first news of the Ebola outbreak was reported, the epidemic was already out of control.

This is one of the few treatment centers in Guinea. It's run by Medecins Sans Frontières, or Doctors Without Borders, an international medical aid organization. It's a haven of humanity and compassion.

The medical staff works in conditions most would find hard to imagine.

COKIE VAN DER VELDE: It's very difficult to interact with people through pairs of gloves. I try to touch people and stroke people, because they won't have had any physical contact with anybody since they've been in there.

When I look in their eyes, and people still understand the situation, I see a lot of fear. If they haven't become confused, I quite often see despair.

NARRATOR: Ebola is an especially virulent disease.

This is what the virus looks like. When it enters the body, it courses through the blood stream, hijacking the victim's own cells to reproduce as fast as it can. Then its progeny rampage on, infecting the endothelial cells that line blood vessels, causing some patients to start bleeding on the inside.

COKIE VAN DER VELDE: They start to bleed from their gums, from their nose. They have terrible bloody diarrhea, vomiting. They feel terrible.

NARRATOR: In these outbreaks, some of those infected manage to fight off the virus and survive. But for those whose immune system isn't strong enough, their vital organs quickly start to fail.

COKIE VAN DER VELDE: Quite often, when you see the blood or they start to hiccup, you know that the end is coming quite soon. You know they've got maybe one or two days left.

NARRATOR: Patients who die usually succumb within 12 days, but the dead body of a victim is still infectious. So anyone preparing the deceased for burial is at a very high risk of catching and then spreading the virus.

COKIE VAN DER VELDE: It's a bit like erasing somebody. You put their body and seal it in a body bag. You take all their possessions and you burn them, and then you clean away their blood and their feces, and then the next patients come.

We allow relatives to come and view the bodies before we seal the bags. So, we bring the bodies to a fence, and we'd always try and put flowers or toys around the face of the child, to make it look pleasanter, if we could. And then the relatives would come and see. And that was always a very hard moment.

NARRATOR: And when Ebola sweeps through a village, it leaves fear and suspicion in its wake.

SANDRA SMILEY: People are very fearful of health care workers, and I can understand. Can you imagine a car entering your village, with people who are speaking a language that isn't necessarily your own, covered from head to toe? And they take one of your loved ones away, only to return the loved one in a body bag. It can be really difficult for people to understand that we're here to help.

NARRATOR: There has never been a more urgent need to find a cure for Ebola, and to understand how it works and spreads.

It was first identified fewer than 40 years ago, and the story of its discovery begins a long way from tropical Africa, in the city of Antwerp, Belgium.

In 1976, a package containing a sample of blood arrived at Antwerp's Institute of Tropical Medicine, where Peter Piot was working as a young scientist.

PROFESSOR PETER PIOT (London School of Hygiene & Tropical Medicine): One day, we received a blue thermos, which contained two vials, actually one was broken, and in some ice…was swimming in there, in water and ice. And it came from Kinshasa.

NARRATOR: The scientists in Antwerp had heard reports of a frightening new disease that had swept through a remote mission station in Central Africa. The specimen of blood came from a Belgian nun who had died there.

After preparation, the sample was studied under an electron microscope.

PETER PIOT: When we saw these worm-like structures coming out of the electron microscope, we were all a bit breathless, frankly, and said, “What the hell is this?”

NARRATOR: There was only one way to find out: go to the source of this mysterious epidemic, the Congo.

PETER PIOT: I really couldn't sleep. I was so excited. We left at 5 o'clock in the morning. I didn't know what to think.

You know, Central Africa is overwhelming. It's like flying over a green sea with, then, a river in the middle. I was just very impatient to get there and to start working.

So, after several hours of flight, so the plane goes down and lands on this red airstrip. And we're landing, and, first of all, the pilots never stopped the engines, because they were so scared and wanted to drop us and go back to Kinshasa.

NARRATOR: The team filmed their expedition, as this rare footage shows. From the airstrip, they headed off to their final destination, the ravaged mission station.

PETER PIOT: And so we arrived there. We stop, and we saw three Flemish nuns, there, and a priest. I said, “I'm Peter Piot. I'm from the Institute of Tropical Medicine, and we're coming here to, you know, to stop the epidemic and to help you.” You know, when you're 27, you think you can really save the world.

And they said, “No. Don't come near. Don't come near, because we're all going to die.”

NARRATOR: Fifteen nuns and nurses and an unknown number of villagers had already been struck down. The team decided to name the mystery virus after the Ebola River that flowed nearby.

Their first priority was to work out how the virus was being spread. They travelled to nearby villages looking for clues.

PETER PIOT: It was already rainy season. Some villages, we could not reach by road, and some we had to walk to, and some we went by a canoe.

NARRATOR: And when they found people who had contracted the virus, many were beyond help.

PETER PIOT: They had this look in their eyes, staring at us in, often excruciating, pain, particularly abdominal pain. They were coughing. Several of them had blood coming out of their nose.

NARRATOR: The scientists noticed that many carriers of the disease were young women who had visited the mission station hospital.

PETER PIOT: What we found was that this was a hospital that had no doctor basically. The nuns and local nurses were running it, frankly in a heroic way, but they had a major shortage of materials including syringes and needles.

NARRATOR: So women who came for prenatal visits often received injections with used syringes.

PETER PIOT: And they were reused and reused and reused.

NARRATOR: The needles weren't sterilized between injections, and it quickly became clear that this was how the virus was being spread from person to person.

PETER PIOT: But then what we also found was that about one week after a funeral of someone with Ebola infection, you could see another outbreak.

NARRATOR: The scientists soon realized that the ritual of washing bodies before burial was also contributing to the spread of the disease.

The team came to an important conclusion. Ebola was spreading through contact with bodily fluids, not through the air. That would be a crucial piece of information in fighting the epidemic.

By early April, 2014, Ebola had spread from Guinea to neighboring Sierra Leone and Liberia, where there is only one doctor for every 71,000 people, compared to the U.S., which has approximately one doctor for every 400 people.

Local health facilities are completely overwhelmed.

The health workers from Medecins Sans Frontières visit a hospital in Monrovia, the capital of Liberia.

COKIE VAN DER VELDE: There was supposed to be a doctor in there who I'd heard had died the day before. And I couldn't find him on any of the beds, so then I checked the, the latrines. And the poor man had died in the toilet and was still there. They hadn't moved him. And apparently he was there for another two days after that, before the burial team came and took him away.

There was a lot of people in the confirmed area who were in great pain and groaning and being sick, or calling out. If Dante had written a Tenth Circle of Hell, this would have been it, I think. You tried to be efficient. Luckily, in a protective suit, no one can see if you're crying, so no one can tell.

NARRATOR: The British nurse, Will Pooley, was already working as a volunteer in Sierra Leone.

As the outbreak spread, he went to one of the worst affected areas of the country to help at a hospital where several nurses had already died, after contracting Ebola from their patients.

WILL POOLEY: Everyone is aware that it could be them next, and it, and, as you were providing that care for those colleagues, you know that you might be risking infection. And so, the team may soldier on, but everyone's…there's fear.

NARRATOR: Then, one night, Will went to bed with a sore throat.

WILL POOLEY: I woke up in the morning feeling very fatigued. My body was aching all over, and I had a headache and a temperature. At lunchtime, I went and spoke to the doctors, and they recommended that I have a blood test, to test for Ebola.

NARRATOR: Later that day the results came through.

WILL POOLEY: When the doctor told me that I was positive for Ebola, obviously having seen what Ebola does to people, it was worrying. I remember my very first concern was having to tell my parents.

Of course I was, I was scared. It feels like you're hosting, hosting a really malevolent force inside your, inside your body. And you…also the knowledge that however I was feeling, especially in the early stages, that the virus could or likely would get stronger, and I would have more of it inside me. And knowing what that would then, what the consequences for my body were of that increasing viral load, the prospect of that was very frightening.

NARRATOR: The fear that Ebola brings with it is very real, yet Ebola is a rare disease. Since 1976, in all the previous recorded outbreaks, fewer than 2,000 people have died. This current epidemic is already worse than all previous Ebola epidemics combined. And with each new case, the risk of the disease spreading even further grows ominously.

In London, a high-level isolation ward at the Royal Free Hospital was on standby, should an infected carrier arrive in Britain. The unit is run by Dr. Michael Jacobs.

MICHAEL JACOBS: This is one of our very special isolation beds. And when a patient arrives in the hospital, we bring the patient into this unit, wearing personal protective equipment and clothing. And we then help the patient into this bed, and once they're in the bed, the whole area becomes separated from the outside, with a controlled airflow going through it.

NARRATOR: Then, in July, the nightmare scenario that health workers had most feared became a reality, not in the U.S., Europe or England, but in Lagos, Nigeria, a city of over seventeen-million people. On the 20th of July, Patrick Sawyer, a Liberian American, collapsed in the arrivals terminal of Lagos airport. He had just landed on a flight from Liberia.

Five days later, he was dead.

Within weeks, the infection spread to 20 people. Eight died.

There was now a new threat in the Ebola crisis, and not only in Nigeria, but now, potentially, anywhere within reach of modern air travel, even the U.S. In Atlanta, the implications were clear.

INGER DAMON: It was a turning point in terms of showing, sort of, the effect that one could see travel, then, through air and spread to a distant country.

NARRATOR: Previous Ebola outbreaks had mostly been confined to remote areas of tropical Africa, but now this epidemic was spreading to big cities and people on the move.

With an incubation time of up to 21 days, Ebola seems poised to spread. So doctors and scientists from around the world have come together on an urgent quest. They're following several different paths, all hoping to arrive at the same destination, a cure for Ebola.

One path started in Uganda. Before this epidemic, the biggest outbreak of Ebola was here, in the year 2000. It was centered around the town of Gulu, in the north of the country. Four-hundred-twenty-five people were infected, but almost half of them managed to fight off the disease.

These are four of the survivors.

Caroline worked as a nurse, treating some of the first patients.

CAROLINE OTTO (Ebola Survivor): There were very many patients coming with headache, diarrhea, and that is how I got Ebola, because there was no protection. We were holding them by our bare hands, without protecting ourselves.

NARRATOR: Walter became ill after he visited a friend, Abedi, who was dying in hospital.

WALTER ODONG (Ebola Survivor): Unfortunately, I touched the bed of the late Abedi. Then, coming home, I never knew that I'd already contracted Ebola, from the bed.

NARRATOR: Abraham, a teacher, caught it from his neighbor.

ABRAHAM LINCOLN OCHORA (Ebola Survivor): I was feeling headache, diarrhea and then vomiting. I think that I was going to die, because they have even put a coffin there on the front of the door. If you died, they will just put you straight away in the coffin and bury you, take you to the burial ground.

NARRATOR: All the doctors could do was to try to ease their pain.

CAROLINE OTTO: I thought I was not going to survive, because Ebola is a deadly disease, and we've got no medicine. When you are infected with Ebola, you have to die, because so many of them died.

NARRATOR: With no treatment available, over half the patients in the Ugandan epidemic died. But those who survived did so because their immune systems somehow managed to defeat the virus.

WALTER ODONG: I remember the doctor said, “Walter has iron blood that fought Ebola very fast,” and I was very… I also smile.

NARRATOR: These survivors play a crucial role in the search for a cure.

Virologist Leslie Lobel, and Dr. Julius Lutwama, have been studying them and the survivors of other outbreaks, for 12 years.

DR. LESLIE LOBEL (Ben-Gurion University of the Negev): We're trying to discover what in their immune response enabled them to survive. We're trying to identify, which we've already done, those with a very successful immune response that can actually fight off the virus, what we call neutralize the virus.

NARRATOR: Today, they are driving to Gulu, to add to their collection of survivor blood samples, looking for clues to understand how their strong immune responses work to counter Ebola, and to learn whether they have gained any lasting protection.

LESLIE LOBEL: The survivors that we follow in Gulu and in other parts of Uganda, we view these people as the blessed ones, those that have the gold in their blood that enabled them to survive this serious disease.

NARRATOR: At the Gulu hospital, Caroline and some of the other survivors have gathered to meet the researchers.

DR. JULIUS LUTWAMA (Uganda Virus Research Institute): Good morning, ladies and gentlemen. This group of people, you, are the only people in the whole world who have been followed up after having had Ebola for a long time. So, we have come again to find out whether your antibodies are still at the same level or whether there is a decline.

NARRATOR: Antibodies are proteins in the blood that the immune system uses to fight germs like the Ebola virus.

LESLIE LOBEL: The basic premise of what we're doing is to take blood from the survivor group, identify those with the strongest immune response, isolate the antibodies from their blood that will kill the virus, reproduce it in our lab and produce a therapeutic from that.

We're also studying the long-term effects of Ebola virus on the immune system or the persistence of immunity in Ebola virus survivors.

NARRATOR: Some survivors have especially strong immunity, at least against the strain of Ebola they caught. Learning how that immunity works is the focus of this research, which they hope might turn into a treatment or a vaccine.

DR. JOHN M. DYE (United States Army Medical Research Institute of Infectious Diseases): What we don't know right now is what is so special about these people. What is so special about their immune system that has allowed them to control the infection and live?

NARRATOR: The blood samples need to be rushed back to Entebbe, halfway across the country, within 12 hours, before they start to degrade. There, at the Uganda Virus Research Institute, the team begins the process of extracting the antibodies.

LESLIE LOBEL: We want to learn from nature what the strongest antibodies, or the protein molecules, in the blood that we know can actually prevent infection and can be used therapeutically.

NARRATOR: Once the antibodies are identified, they are then tested against live Ebola virus in cell cultures and will soon be tested in infected animals.

LESLIE LOBEL: At this point, we've isolated a whole library of human antibodies from survivors of Ebola virus disease. In the future, maybe in three to five years, these can be then tested in humans, in terms of safety testing, so that they can be used as passive vaccines or treatments.

NARRATOR: The work in Africa continues. In the United States, scientists are also on the hunt for a cure. The development of an experimental drug has recently been accelerated by the plight of two American missionaries in Liberia.

When Ebola hit, Dr. John Fankhauser was helping run the hospital, in Monrovia, where they worked.

DR. JOHN FANKHAUSER (ELWA Hospital): We had anywhere from two to six patients every day.

NARRATOR: Dr. Kent Brantly was director of the Ebola unit.

JOHN FANKHAUSER: He had a deep commitment to the people of Liberia. He really connected with patients.

NARRATOR: Nancy Writebol was a nurse assistant, responsible for decontaminating hospital staff.

JOHN FANKHAUSER: Nancy was the kind of person who had a level of energy and enthusiasm that really affected everyone around her.

NARRATOR: After treating dozens of Ebola patients, Dr. Brantly caught the virus himself. Then Nancy was diagnosed with Ebola, as well.

JOHN FANKHAUSER: I was very surprised, and then I also just had a deep sense of concern, because I knew that Ebola was a disease in which the mortality was very high. You know, these were two friends of mine who were facing a deadly battle.

NARRATOR: But Dr. Fankhauser was aware of a potential ally in the fight, in the form of a promising, but untested, new drug.

JOHN FANKHAUSER: We had, of course, heard of novel therapies for Ebola. We were also aware that there were some doses of one of these novel therapies in Africa, in West Africa.

NARRATOR: By an amazing stroke of luck, in nearby Sierra Leone, Dr. Gary Kobinger was helping diagnose cases of Ebola. And he had brought with him an experimental drug called ZMapp. He had been working on it for more than a decade, though it was still untested in humans.

DR. GARY KOBINGER (National Microbiology Laboratory, Canada): The goal was to bring it there, keep it there, and then bring it back here, and then test it to see the potency.

NARRATOR: The story of how the ZMapp drug was developed began 15 years ago, when Gary Kobinger was working on a gene therapy for cystic fibrosis. He needed a way of transporting a healthy gene into lung cells to replace a defective one.

GARY KOBINGER: We wanted a virus that can basically be that vehicle that brings the altered gene into that defective cell, the virus' transport mechanism, a little shuttle.

NARRATOR: Gary began looking for a virus that was most effective at entering cells. He settled on a surprising one.

GARY KOBINGER: The Ebola virus is a very long virus. It's like a string, and it attaches to cells, and it wraps into cells, a little bit like Velcro®, if you want, will stick to the other part of the Velcro.

NARRATOR: Like other viruses, Ebola enters cells in the body using spikes on its surface. These spikes are special proteins that bind the cell membrane. When the virus latches on, the cell is forced to engulf it.

GARY KOBINGER: It's swallowing the virus, if you want, and bringing it into the cell.

NARRATOR: As Gary began using Ebola spikes to transfer genes, he had another idea: perhaps the spikes could be used against the virus itself.

GARY KOBINGER: The fact that the virus is using the spike to enter cells and to start growing and multiplying itself, if you can stop that, if you can mount, if you can stimulate your defense to attack that same spike, then your defense will attack that same protein that allows the virus to enter the cells.

NARRATOR: It was an interesting hypothesis.

GARY KOBINGER: I knew it would be a long road ahead, and, basically, you know, at the time, everything had failed. Nothing had worked to protect against Ebola virus.

NARRATOR: This is Canada's National Microbiology Laboratory, in Winnipeg, a high security facility that's home to some of the world's most deadly viruses, including Ebola.

GARY KOBINGER: The one thing for sure is you don't get a second chance, if you have an exposure, because your barrier has been compromised. And, for this, it means that you could eventually have been exposed to a high dose, so the likelihood of having a fatal outcome from lab exposure is very high.

I will, you know, take the time to be calm before going in, empty my head completely of every little preoccupation I may have during that day or in the past or in the future. And I go in just concentrating on what I have to do.

NARRATOR: His first idea was to get the body's own immune system to fight the Ebola spikes. By exposing monkeys to the spikes, he found they produced antibodies against them, some of which could be crucial.

GARY KOBINGER: There were antibodies specifically targeting the spike of Ebola. So these antibodies, if you look at those antibodies in an animal, and if you get this threshold or above, you can predict with 99.98 percent accuracy that the animal will survive, in normal primates.

NARRATOR: It was an important milestone.

GARY KOBINGER: And so, when we started seeing that those antibodies were so important, then yes, for sure then we started thinking, “Well, the antibodies are likely to work. It's just how we're going to use them is the question.

NARRATOR: Dr. Kobinger received a message from the missionary organization Dr. Brantly worked for. It was an urgent request for the experimental drug ZMapp.

GARY KOBINGER: It was from inside, a request from the heart, a request from the soul. Without being emotional, the request was formulated in a way that, anyway, pinched a chord inside me.

NARRATOR: The drug had shown a lot of promise in monkeys but had not yet undergone clinical trials, the only true test for a drug's safety and efficacy. So there was no way to know how any patient, much less a patient already weakened by disease, would tolerate it.

GARY KOBINGER: My first reflex, and this is what I did, I warned against the unknown safety status of the drug.

NARRATOR: There were other concerns, too.

GARY KOBINGER: There was a lot of ethical questions. You know, “Why them? Why not the kids I'd seen dying in front of me?” You know, but you feel, at one point, that either you have to stand or you have to step aside. And, at that time, I thought my…what I had to do, the right thing for me to do was to step aside.

NARRATOR: And everyone concerned had to weigh the risks of taking the untested drug against an unknown benefit. A decision had to be made, and fast.

JOHN FANKHAUSER: My rationale for offering the drug was that, as a group of medical providers with all of the medical information that we had, we had the feeling that it had a very high probability of being of value to Kent and Nancy. And then the decision to give the medications was really made after a discussion with Kent and Nancy, and after they expressed their interest in getting the medication.

NARRATOR: But there was a problem. There were just three doses of ZMapp available, the course of treatment for just one person.

GARY KOBINGER: Yeah, that was a very difficult moment also. How do you save two people with one treatment, because that's all we had?

NARRATOR: This seemed an impossible choice, but the two patients themselves made it.

JOHN FANKHAUSER: They were both willing to sacrifice the medication that was beneficial to them, in order to help their colleague and friend.

NARRATOR: But despite the patients' willingness to share, evenly dividing the medicine would likely mean that neither would benefit. So doctors made a momentous and potentially risky decision: to administer most of the drug to Dr. Brantly, whose illness had just taken a dramatic turn for the worse.

Nancy Writebol would receive a smaller amount. For a full course, she would have to wait for a return to the U.S.

Still, injecting an untested drug in any patient was a huge risk.

GARY KOBINGER: This physician, at one point, had to decide, “Am I really going to inject this thing that I don't know much of?” There was a lot of unknown for that person, a lot of pressure, and so, I think, to me, that, that's a hero.

NARRATOR: Kent Brantly and Nancy Writebol were brought back to Atlanta. Her treatment continued with ZMapp. Dr. Aneesh Mehta was part of the team who would treat them.

DR. ANEESH MEHTA (Emory University School of Medicine): The information we received is that the first patient had received a dose of an experimental medication and seemed to be improving after that medication.

We did also hear that the second patient also had received a dose of that medication and seemed to be stable at that time.

NARRATOR: The fear was that because both patients were ill with Ebola, the drug would not be enough to save them.

In his research, Dr. Kobinger had discovered there were antibodies that could defeat Ebola, but often, after infection, the body can't produce enough of them, because Ebola overwhelms the immune system. He needed to find a way to reverse this process.

GARY KOBINGER: The virus is so fast that it kills you before you get that level of antibody that can protect you. So, we thought that we will inject those antibodies, as our body would do, but we would inject them faster, if you want, than what the body does.

NARRATOR: Dr. Kobinger exposed mice to the Ebola spikes to produce different antibodies. The aim was to try and find a combination that would slow down the spread of the virus when given to monkeys.

GARY KOBINGER: So, we're going to put a lid on the infection, and we're going to buy time. We wanted to let the host have enough time to build that protective immune response, themselves.

NARRATOR: In monkeys, the antibodies latched onto the Ebola spikes and stopped them from sticking to cells. Unable to pass through the cell wall and reach the interior, the virus can't replicate.

By slowing the spread of the virus, the immune system is able to catch up, producing more of its own antibodies to defeat the virus. This one-two punch proved decisive.

GARY KOBINGER: We saw survival when we were starting this treatment at 24 hours, which was very late. From there we started thinking, “Well, maybe we can make it better.”

NARRATOR: By giving the monkeys two more doses, three days apart, the animals didn't just survive, they recovered.

GARY KOBINGER: One day didn't mean anything, but when we were three, four, five, six days in, a week, two weeks, and people were coming to see them, they wanted to see how they looked, and they wanted…so that was a very unique moment, I think.

NARRATOR: The treatment saved 100 percent of monkeys infected with Ebola.

GARY KOBINGER: For sure it was exciting. No, I can tell you some images of people clapping in one another's hands in Level Four, when we started seeing those animals not only surviving but doing so well. It's like barely they were infected.

NARRATOR: As other scientists helped refine the cocktail of antibodies, all of the monkeys survived, even when treatment started five days after infection.

This combination of three antibodies is the drug ZMapp.

GARY KOBINGER: When we saw that, after symptoms had been detected, that we could still cure 100 percent of them, to me this was a cure, clearly. Yes it was.

NARRATOR: Fortunately, there was a small supply of ZMapp available in the U.S. After finishing a course of the drug, both missionaries recovered.

Scientists cannot yet say whether it was the drug, the excellent care that both received or a combination of both that made the difference.

DR. KENT BRANTLY (Ebola Survivor): I'm thrilled to be alive, to be well and to be reunited with my family.

NARRATOR: Amid the relief, there were questions.

Why had the two Americans been given the experimental drug ahead of the African Ebola patients they were there to help?

JOHN FANKHAUSER: If these medications were given to an African, by a team that was of a different culture and a different background, and that would have led to a bad outcome, we would have been harshly criticized.

I think this was a time where we could offer these medications with true informed consent. Now, that being said, I am a complete believer that we need to strive for equity in this outbreak, that Africans should have access to the medications that are available to expatriates.

NARRATOR: Demand for the experimental treatment skyrocketed and the small supply of the drug dwindled. Now, the race was on to produce more. Charles Arntzen, at Arizona State University, developed the method currently used to make it.

This isn't really a greenhouse of tobacco plants. It's a production line for drugs.

CHARLES ARNTZEN: Any time you want to make a protein drug, a vaccine, you have to have a living system to manufacture it. So, for the last five to eight years, now, we've really focused on viruses which infect the tobacco plant. We take some genes out of that virus, put back in some genes that we want, and then, literally, inject into the leaf tissue, so that every cell starts a viral infection. And as that virus replicates, it makes a copy of the protein that we're interested in.

NARRATOR: These proteins are the antibodies that go into ZMapp. Like all living things, tobacco plants produce proteins in their cells. Their D.N.A. tells them which proteins to make. To turn the plant into a factory, making antibodies for ZMapp, a plant virus carries extra D.N.A. into the leaf. The recipient plant cells then produce the antibodies.

This was the method used to make the ZMapp given to the American missionaries. But as the outbreak continues, will this technique be able to produce enough to help the thousands who desperately need it?

CHARLES ARNTZEN: The actual production run that made the protein that was used with the individuals in Africa was probably about 10 days in the tobacco plant and maybe another 10, 10 days to two weeks to purify the protein out of the plants.

To scale this up, to make a thousand doses or 5,000 doses, that's much harder to come up with a timescale for that, because it's equipment-driven, it's people-driven. And to try to scale something up from making 50 grams, as we might do now, to making kilogram amounts, that's, that's like trying to get a little hybrid to compete with a Maserati, in terms of taking off, on a timescale.

NARRATOR: Producing enough of the drug to cope with the epidemic in Africa will be a challenge. Drug companies are reluctant to invest the enormous amount of money required for research and development on a drug that has little potential for profit.

TV NEWS: William Pooley, the first person from the U.K. to contract Ebola in West Africa, is in a special isolation unit, after being flown back to Britain by the R.A.F.

NARRATOR: British nurse Will Pooley was to be offered the last available doses of the drug.

WILL POOLEY: Dr. Jacobs very clearly told me the risks associated with using ZMapp and some of the unknowns around the use of the drug.

MICHAEL JACOBS: Well, it's a very unusual situation for us to use a drug which actually hasn't been used in humans extensively before. Most drugs have been through a very prolonged regulatory process to check their safety as well as their effectiveness.

WILL POOLEY: I was very keen to use the drug, and I said this to Dr. Jacobs, that I, I want to go ahead and use it, because the ZMapp seemed to be the only, my only option.

After the first infusion finished, very soon afterwards—we don't know whether this was due to the ZMapp or not—but I, I started feeling considerably better. My temperature had come down, I felt a lot more comfortable.

MICHAEL JACOBS: We were cautiously optimistic, once the viral load began to fall.

WILL POOLEY: He told me about what my blood result had been over the last few days, and then, with a bit of a smile on his face, told me that my virus load had diminished to undetectable levels. So, effectively, I was, I was free of the, free of the virus. And on telling me, obviously I was, I was over the moon.

MICHAEL JACOBS: From a personal point of view, I was both exhausted and elated at the outcome.

WILL POOLEY: People worked so hard to get me those, those last doses of ZMapp. And I want everyone to be able to have the care that I received, and the treatment that I received, because it makes a difference in whether you live or die. To know that people, just because they're living in West Africa, don't get that is, is heartbreaking.

NARRATOR: Months into the epidemic, the death toll keeps rising, and health workers say many more people are dying than the official figures would indicate. Behind each case lies a very human story.

COKIE VAN DER VELDE: One of them was a man in his 40s. He was quite a character, and he was called Horatio. His situation, it gradually deteriorated. He was in the most awful pain and rolling on the floor, and very, very distressed, but, unfortunately, the pharmacy that was there didn't have much in the way of sedatives or sleeping pills or anything for palliative care.

And I must admit, at 10 o'clock at night, myself and the rest of the M.S.F. team were going round pharmacies, trying to find medicine for him, but he died. So he died on his own, without any pain relief at all.

NARRATOR: Around the world, scientists are urgently continuing the search for a cure. Haunted by horrific, worst-case scenarios, public health officials are ramping up their efforts on the ground, as countries like the U.S. are pouring more resources into the fight, and not a moment too soon.

In late September, 2014, a man who had returned from West Africa just days before, turned up in a Dallas emergency room with a fever and other symptoms. Though he reported that he'd recently travelled from West Africa, no one acted on that information and he was released.

A few days later, he was back, and this time he was given a test for Ebola, which came back positive. His is the first case of an infected person entering the U.S. not already under medical care.

His story reminds us that, while progress is being made, the stakes are growing ever higher in the struggle to stop the deadly Ebola virus from further ravaging lives in West Africa and beyond.