We Thought Cancer Was Uncontagious. We Were Wrong.

Kind: captions Language: en Cancer is one of the most terrifying diseases on Earth. It's unpredictable and often impossible to cure. It's only controlled, but there has always been one comfort. You can't catch it. It comes from your own cells going rogue. At least that's what we thought. That all changed in 2013. A man was being eaten alive by aggressive tumors >> [music] >> that belonged to a different species entirely. What doctors discovered next would force them to question everything they knew about the disease. In January 2013, a man was rushed to a busy hospital in Medellin, Colombia. He was in bad shape, suffering from rapid weight loss, a persistent fever, and a medical history of HIV. It had been manageable with medication, but he had stopped taking it a few months earlier. Any one of these factors could have caused a health emergency or all of them combined. HIV is not uncommon in Colombia, and unlike in many countries, the combination of poverty and poorer medical infrastructure means fewer people keep up with the health and medication regimen needed to survive it long term. The initial symptoms of fatigue, a cough, and weight loss were compatible with his diagnosis, but the swelling was an unusual side effect. [music] And they were even more shocked when they looked closer. It was clear that the man was seriously ill. So, a battery of tests was administered. The man's HIV status revealed that his viral load had skyrocketed. Stool samples were taken, and they revealed a tapeworm infestation in his digestive tract. Specifically, it was the Hymenolepis nana, the dwarf tapeworm, a common species in humans, especially in temperate zones. But the most concerning part of the man's condition showed up on the x-rays. He was riddled with tumors all through his body. The man's breathing was highly labored, which didn't conform with other causes for his condition. X-rays of his lungs and lymph nodes revealed that the apparent cancer was concentrated there. While some tumors are benign and they can be safely removed, an abundance like this usually means malignant cancer, and biopsies were quickly taken. Upon examining the cancer cells under a microscope, the case continued to become more and more bizarre. The cells didn't resemble standard cancer cells at all. In fact, they didn't seem to be human. The man quickly deteriorated. The strange foreign cells had caused golf ball-sized tumors in his lymph nodes, making it difficult for him to even turn his head. His breathing [music] became more and more labored. The standard treatment for acute cancer, chemotherapy, wasn't going to be any use here. Mainly because no one knew how the chemical cocktail would work against a parasitic infestation. But his legacy as one of the strangest medical case studies in history was just beginning. A true medical mystery is unusual in a hospital. To those trying to save a life, it can be a nightmare. To pathologists, it can be a dream come true. And as soon as the more powerful microscopes were called into service, it became clear this was not a case that would be solved in the hospital. The biopsy was one of the most baffling results anyone at the hospital had ever seen. These tiny cells were up to 10 times smaller than a standard cancer cell, creating a scan that was confusing at best. The hospital [music] had sent the scans out to pathologists and hospitals and research centers that they were in contact with. One of those scientists was Dr. Atis Mühlenbach, a researcher and pathologist at the Centers for Disease Control and Prevention. Even for Mühlenbach, this was a bizarre sight. The samples from the biopsy didn't match any condition he had ever seen. They looked like sheets and clumps of tightly clustered cells that behaved completely differently from human cancer cells. In fact, at first he thought it was a slime mold. There is only one thing that was clear. The cells were on the move. Like other cancer cells, they were reproducing fast. They were also crowding out their competitors in an even more life-threatening way than most human cancer cells. To Mühlenbach, this was potentially an existential threat. In Columbia, the man continued to linger in the hospital, his condition a mystery. With his apparent cancer not matching any medical records, the hospital was left to focus on palliative care. It would be over 2 months before the first breakthrough in the case. The CDC ran broad-range PCR testing on samples taken from the Colombian hospital, screening for genetic material across a wide range of possible causes. But when the DNA from the tumor tissue finally came back, it didn't match anything human. Yes, the man had cancer, but it wasn't his cancer. It was from the tapeworm infestation inside him. For the first time, a foreign entity had managed to seemingly transmit cancer to a human being, creating a new and bizarre disease. >> [music] >> That result changed the entire direction of the investigation, turning a routine search for disease into something far more unsettling. In 2013, Colombian doctors tried to diagnose him with small cell lung cancer. Sure, the cells were smaller than average, but it was close enough. By the time the diagnosis was first unlocked and the tapeworm DNA was identified, it was already too late. The man's condition had gone seriously downhill as the cancer had spread through his body. He was bedridden, barely able to breathe, and after 72 hours, he passed away before a treatment plan could even be conceived. But the mystery would linger on. It would outlast the man by nearly 300 times his remaining lifespan. He lived only three more days after the diagnosis, but it took scientists [music] 2 and 1/2 years to complete the full genetic sequencing needed to map the tapeworm's cancer mutations. Over the course of those two years, several different tests came back positive for human DNA, but they were all faulty. The tapeworm cells came just close enough to small cell lung cancer that the false results were passed on multiple times. Scientists missed the clues that were right in front of them. But while doctors and researchers were looking at the man's lungs, the real horror was happening inside his intestines. The tapeworm is one of the most disgusting creatures alive. It infests the digestive tract of a person, feeding off [music] the same nutrients they eat and growing. This has led it to develop a morbid fan base as a weight loss tool. Of course, unlike diet and exercise, the tapeworm is actively dangerous to its hosts. Most tapeworms reproduce through human waste. >> [music] >> Tapeworm eggs wind up in the feces, which then enter the sewage system, and the eggs get eaten by other animals. The tapeworm larvae hatch in these intermediate hosts before finding new human hosts for the long adult life cycle. It is a disgusting life cycle, but a manageable one for most people, except for one species, >> [music] >> the dwarf tapeworm. It rarely exceeds 1 and 1/2 inches long and 0.04 inches wide. >> [music] >> That makes it much harder to detect and much harder to get rid of. Like other tapeworms, it attaches itself to the lining of the digestive tract using hooks and suckers. It enters the human body through contact with its eggs, often [music] spread through contaminated food. But what it does once inside is what makes it far more dangerous than expected. It keeps [music] going. In a hospital host, the eggs can be laid, hatch, and start the cycle anew. It's uncommon for a single person to have more than one of another species of tapeworm, which allows the parasite to grow to disturbing lengths in some cases. But it's far more dangerous when they do have competition because a dwarf tapeworm population can grow out of control if [music] it's not treated. That's when it starts having serious impacts on the functioning of the body, leading to rapid weight loss as the population skyrockets. Like any cell, tapeworm cells can mutate when they reproduce. There's always the risk for cancer in any organism, but when a smaller organism develops cancer, it's much less likely to be noticed by humans and the infected [music] specimen is likely to die off quickly. But this time, the environment was a little too hospitable. Due to a lack of treatment and access to resources, the man who showed up at the Medellín hospital in 2013 had allowed a colony of tapeworms to develop inside of his gut. At some point, one of them developed cancer, and before it could die, its mutated cells were transferred into him. The parasite was effectively growing its own tumors while living inside another organism, and those tumors were reproducing alongside it. Over time, something even stranger appeared to happen. The cancer seemed to realize that the host might make for a better place than the tapeworm. And so began one of the most disgusting jailbreaks in medical history. But how did the cancer-riddled cells of a foreign organism survive in the human immune system? The fact is, we all have parasites. At any given moment, the human body is home to billions of microscopic organisms >> [music] >> that perform a mutualistic role. While there's no average estimate, worms in the digestive tract and mites on the skin and hair are incredibly common. >> [music] >> In most cases, they either quietly coexist in the body without causing harmful effects or are eventually killed off by the human immune system. But this wasn't the average person. The tapeworms and their cancer was what eventually killed the man in Medellín, but his fate had been written long before that. At the root of his illness was his HIV-positive status. In the modern day, many people with HIV live completely normal lives, >> [music] >> save for a regular medication regimen. This allows them, maintaining the regimen, to get to undetectable status, where the viral load can't be passed on to lovers or future children. But if that regimen is dropped, well, things go wrong fast. In the past, HIV was a death sentence because it led to AIDS, which ripped its way through the human immune system, killing [music] off resistance to common illness. Very few people who died of the AIDS epidemic were killed off by the virus itself. They died of common respiratory ailments or infections that a healthy person could have fended off. The virus damages the CD4 cell count, also known as white blood cells. Tests showed that the patient's white blood cell count was only around 2% [music] of the amount a healthy person would have. An army that goes to war with 2% of its men is going to get slaughtered. An untreated tapeworm infestation in a healthy person would be noticeable quickly due to the weight loss, >> [music] >> but it would likely stay in the digestive system. That's not what happened here. With the natural human defenses so weak, the tapeworm's mutant cells were able to infest the walls of the intestines [music] themselves. From there, they started flowing smoothly through the bloodstream. Soon they were in the lymph nodes and his lungs reproducing. While the species of the tapeworm itself was still [music] confined to his digestive tract, the mutant cells had found a new home, one that was incompatible with the host's continued survival. And the tragic part is all of this was avoidable. It's easy to assume that HIV has been, if not cured, managed. For most people in the United States and Europe, their HIV medications are covered by their insurance and they can get on with their lives with careful maintenance. But around the world, approximately 630,000 people die of AIDS every year. In some countries, there simply isn't the infrastructure to ensure proper health care, with many relying on programs like US Aid to make access possible. In others, those with HIV are afraid to come forward, but the largest cause of this death cycle is simply poverty. Many people in countries like Colombia can't afford the drugs if they're not properly covered. While we'll never know if this was the case for the victim, the lack of maintenance of his anti-HIV regimen opened his body up to infestation. But that could have been prevented, too. Tragically, there's a drug named praziquantel, which is used to treat a wide array of parasitic worm infections. It's used to clear up infections in pets, >> [music] >> but it can be used to cure humans as well. It's commonly prescribed for treating tapeworm infections, but obtaining [music] it still requires both awareness of the condition and access to medication. In this case, the man had neither. The drug typically costs between 7 and 20 cents in many developing countries, making it one of the most affordable treatments available. But it was still out of reach when it mattered the most. [music] In this case, a tragic series of misunderstandings doomed to the patient. No one knows if the man was too far gone to be saved when he came [music] in. His viral load due to HIV was spiking, and it may have been too long without treatment to turn it back effectively. But the tapeworm infestation that ultimately led to his death could have been had for less than a single bottle of water. If this man lived in a country with a lower poverty rate and a more stable health care system, he likely would have been saved long before things reached this point. He would have been under the care of a physician monitoring his HIV treatments who would have reached out to him long before he went without pills for months. Once he came in with his tapeworm infection that had turned into a foreign cancer, access to world-class pathologist meant nothing. No hospital in the world could have diagnosed it earlier, not without specialized help. Something like this had never happened before. And the scariest thing is, this is going to happen again. >> [music] >> When people read the bizarre case study of the man who got infected with tapeworm cancer, the question on many of their minds was, could it happen to me? And the answer is, no, but also yes. The horrors that befell this man were a mix of failures on many different levels. His health [music] had been allowed to deteriorate to the point that the infection raged out of control. Then his hospital lacked the resources to diagnose and treat him quickly. And the distance and lack of hands-on access hampered the CDC's efforts in diagnosing him. H. nana is one of the most common parasites around the world, infecting up to 75 million people around the world each year. For many of them, it'd be a little more than an annoying infection cleared up with a regimen of pills. For others who don't have access to that, it'll be a persistent sickness that may shorten their lives. But the pool of 75 million, roughly the equivalent of the combined population of the United Kingdom and Ireland, is likely to have a large number of people with HIV in it, especially in developing countries. Now, every one of them could be vulnerable. With what is known now, the case of the man with tapeworm cancer was not the beginning of a new kind of parasitic epidemic or a freak mutation taking over the species. Instead, the parasite was doing exactly what it always does, feeding, growing, mutating, and reproducing. The difference was the environment inside the host, which allowed those processes to spiral unchecked. The outcome was rare, disturbing, and fatal for one man, but it also raised a A concern. Under the right conditions, similar vulnerabilities could exist in other patients around the world. The worst-case scenario that many feared when news of the strange case broke hasn't come to pass, thankfully. There is no new form of cancer that's just jumped from tapeworm to human. Instead, what we're discovering is a disturbingly new vulnerability in our own body. If our natural defenses get low enough, we become vulnerable not just to our own cells turning on us, but to parasites infecting us with their own. And that means we might have to rethink what cancer actually is. For the first time, we've seen a foreign cell grow in a person, use their blood and biome to grow and eventually kill the host. This wasn't a planned parasitic infestation. It was the equivalent of someone going to an all-you-can-eat buffet and eating themselves sick. The man was especially vulnerable, and the mutated tapeworm cells were especially voracious. But, if it can happen once, it can happen again, and pathologists everywhere will be looking at every biopsy a little more carefully, just in case it's not a human disease they're dealing with. This isn't the only medical horror story involving a parasite. Some take over completely. Watch most painful parasites that infect humans to get the gory details, or click on this video.