The Deadliest Virus on Earth

In the 1970s thousands of Chickenheads rained  from the sky in Europe, making foxes and other   wildlife confused and very happy. Why? They were  filled with a vaccine to fight the deadliest   virus known to humanity – since the 1930s  a rabies epidemic had been sweeping across   wildlife populations in Europe and humans wanted  to finally get rid of the virus once and for all. Rabies is named after Lyssa, the  ancient Greek spirit of mad rage,   and has been haunting us for at least 4000  years. It can turn animals into angry beasts   and humans into zombies that fear water. But  what makes Lyssa fascinating is not just how   bizarre and deadly its infection is, but also how  incredibly good it is at avoiding our defenses. Viruses exist on the edge between life and death,  hardly more than a few genetic instructions that   need living cells to multiply. The lyssavirus is  simple even for a virus: It has only five genes,   that is the instructions for five proteins that  let it solve complex problems: Infect a mammal,   avoid its immune system, travel to its brain,  make more of itself and infect new hosts. Let's see what happens if you get infected. It all starts with a bite, most likely by a  dog carrying millions of viruses in its saliva,   pushing them deep into the tissue. The goal is  your nerve cells, your neurons. They are living   electrochemical wires, transferring signals  throughout your body, and can stretch for up   to 1.5 meters, with their cellular machinery  on one end and a terminal on the other. The terminal is where cells talk to each other,  by passing chemicals that convey information.   Lyssa probably binds to the receptors  that are crucial for this process   and slips inside the unsuspecting nerve cells. Inside, the virus has to solve a big problem.  It needs to get to the cellular machinery to   take over the cell and make more viruses  – and because neurons are pretty long,   this can be far away. There  is a solution at hand though: Cells have microtubules spanning their  insides that give them structural integrity.   But they also provide a track system  for a specialized delivery system:   Dynein motors are actual motors that use energy  and deliver packages. They are made from 50   different proteins, ten times more than the virus,  and look like a little pair of shoes. Lyssa uses   one of its five proteins to hijack this amazing  system and order it to head for the nucleus. What is the immune system doing to prevent  all of that? Well, unfortunately not much. Usually when a virus attacks your civilian cells  are crucial in activating your immune response.   They notice that they have been infected and  release hundreds of thousands of a special family   of proteins: The interferons that, well, interfere  with viruses. We’ll have to simplify a lot,   but in a nutshell, Interferons alert your  immune system to make antivirus weapons.   But they do much more: they tell civilian  cells to turn down their protein factories   for a while – which means that viruses  can’t replicate efficiently anymore. And interferons tell your cells to become super  transparent, which is important, because how   can your immune cells notice that your civilian  cells are infected when viruses hide inside them? Your body solves this by creating display windows  into their insides, called MHC class I molecules.   Cells constantly produce stuff to stay alive,   and to showcase to your immune cells what is  going on inside them, they take random samples   of their products and put them into these  tiny display windows to give a peek inside. Interferon tells your cells to make WAY more  display windows and become super transparent.   If a cell is infected and forced to make virus  parts, your immune cells will see these parts   in a window and order the infected cell to  kill itself – and all the viruses trapped   within. This is one of the most powerful  methods of wiping out a viral infection. Unfortunately Lyssa blocks your neurons  from making interferons and stays basically   invisible to your immune system. In contrast  to many other viruses, when it replicates,   it doesn’t kill its host, which  would also trigger alarm systems.   Instead it stealthily jumps from neuron to  neuron, very slowly making its way to your brain. This phase can take weeks to  months and very rarely even years   and depends on a bunch of things, like if the bite  was in your face or foot or how many viruses got   into your muscles. Lyssa is a patient monster.  Until it reaches its goal: Your brainstem. Finally, the immune system catches  on that something isn’t right   and reacts. It dispatches some of your most  powerful antivirus cells, Killer T Cells,   to seek and kill infected cells and wipe out the  enemy. In other viral infections this would be a   turning point, but in rabies the T cells are  rushing towards their doom. Simple Lyssa with   its 5 proteins plays a uno reverse card, using  the immune system’s ingenuity against itself. Your central nervous system is a very fragile  part of your body and so the immune system has   to be very careful. A few haywire immune  cells in your brain is a quick way to die.   So they aren’t free to enter your nervous  system, they have to be be invited in   and can be kicked out. To protect themselves, your  nerve cells can order T Cells to self-destruct,   if they think they are overreacting. And Lyssa  figured out a way to make infected neurons express   this order. So as your powerful defense cells  arrive – they are ordered to commit suicide.   Now the virus infiltrates the brain stem. Once  this stage is reached you are going to die. How Lyssa Kills One of the most irritating things about  the Lyssavirus is that we still don’t   know exactly how and why an infected person dies. Our usual idea of viruses causing  damage is by multiplying rapidly,   killing their host cells once they have made  enough copies, triggering a massive immune   reaction that also does a lot of damage. But  this doesn’t seem to be what happens here.   Brain tissue of rabies patients shows  minimal, sometimes non-existent damage.  Instead of murdering everything in sight, it  is currently thought that lyssa wreaks havoc   by messing up the neuron communication inside your  brain, so much so, that it can’t function anymore. It attacks the brain and leads to symptoms  like confusion, aggression and paralysis.  Now the virus begins to leave. Still traveling  through neurons, it migrates away from the brain   and heads for the salivary glands. This is  remarkable, because after traveling in one   direction the virus reverses its course. After  decades of study we don’t know how this works.   Lyssa ends up saturating your saliva  ready for the irate mammal to bite another   and repeat the cycle. While this seems  like the beginning of a Zombie outbreak,   luckily there are no known cases of a human  biting another and spreading rabies this way. Now the end is near. You are rapidly developing  encephalitis, a swelling of the brain with many   unpleasant neurological symptoms, from lethargy  to paralysis. Slowly at first, and then suddenly,   organ after organ fails as you slip into a coma.  There is no known effective therapy, barely anyone   has ever survived Lyssa once symptoms begin to  show. It is by far the deadliest virus we know. Except, there is actually something  that could save you – a vaccine.   Rabies was one of the first diseases  humans developed a vaccine for.   As vaccines do, it prepares your immune system for  a future attack, so it has the right weapons ready   in high numbers. The horrific tricks of simple  Lyssa don’t work once you are vaccinated. And the   vaccine is special for another reason – because  Lyssa is so slow in the first few weeks, it can   be given to you after you have been exposed. So  you can still be vaccinated after you have been   bitten by an animal. Which is super important  if you’ve had contact with a sick wild animal,   say a bat, because you often don’t  even notice a bite from tiny teeth. Rabies is a monster. One that has followed  our species around for thousands of years,   that our ancestors were terrified of and rightly  so. It still kills around 60,000 people each year,   almost half of them children. We are far from  eradicating this monster – It lurks in the   shadows, in forests and animals of all kinds,  ready to return in greater numbers if we ever   forget how to keep it at bay, or if we continue  the trend of being suspicious of vaccines. Let us hope that one day  humanity slays this monster,   so it can become like most  monsters: Part of our imagination. There are much deeper levels  of knowledge to explore about   rabies than the glimpse we just showed you. But digging into sources and  scientific information on your own   can be intimidating. So we partnered with our  friends from Brilliant to create an interactive   course with hands-on lessons to guide you through  some of the concepts we showed in this video.   Brilliant is an interactive learning  tool with over 60 courses in math,   science, and computer science. They make  science accessible with a hands-on approach.   Think of it as a one-on-one tutoring version  of a Kursgesagt video. You’ll experiment with   how fast the virus can reach your brain based on  its protein makeup or run simulations on Rabies’   genetic evolution, to explore how mutations  created the deadly virus we know today. You can do things like manipulate energy  to see how black holes are formed,   or control the expansion of space itself to  determine the ultimate fate of the universe. To get some behind-the-scenes-science-coaching  on space and biology and many more topics,   go to Brilliant.org SlashNutshell and sign  up for free. And there’s an extra perk for   kurzgesagt viewers: the first 200 people to use  the link get 20% off their annual membership,   which unlocks all of Brilliant’s courses  in math, science, and computer science. We love to go down a rabbit hole  with our research – Brilliant will   take you by the hand to come along on the ride.

Channel: Kurzgesagt – In a Nutshell

Views: 7,744,862

Keywords:

Id: 4u5I8GYB79Y

Length: 11min 4sec (664 seconds)

Published: Tue Jul 26 2022

Reddit Comments

[u/MadHatter69]

The part with the cells taking random samples of the RNA and putting it on the display blew my mind.

Every single cell in our body is like a tiny organism with a mind of its own, and most of us are completely oblivious to all the complex stuff that's constantly going on inside us working tirelessly just to keep us alive.

[u/Piltonbadger]

Infect mammal > Avoid immune system > Travel to brain > multiply > try to infect new hosts.

Precursor to zombie virus by the sounds of it :\

[u/srhzaa]

they should name more stuff off Greek gods

[u/Math1988]

You are tearing me apart Lyssa.

[u/mittelwerk]

And if the video doesn't scare you, this Reddit classic will:

Rabies. It's exceptionally common, but people just don't run into the animals that carry it often. Skunks especially, and bats.

Let me paint you a picture.

You go camping, and at midday you decide to take a nap in a nice little hammock. While sleeping, a tiny brown bat, in the "rage" stages of infection is fidgeting in broad daylight, uncomfortable, and thirsty (due to the hydrophobia) and you snort, startling him. He goes into attack mode.

Except you're asleep, and he's a little brown bat, so weighs around 6 grams. You don't even feel him land on your bare knee, and he starts to bite. His teeth are tiny. Hardly enough to even break the skin, but he does manage to give you the equivalent of a tiny scrape that goes completely unnoticed.

Rabies does not travel in your blood. In fact, a blood test won't even tell you if you've got it. (Antibody tests may be done, but are useless if you've ever been vaccinated.)

You wake up, none the wiser. If you notice anything at the bite site at all, you assume you just lightly scraped it on something.

The bomb has been lit, and your nervous system is the wick. The rabies will multiply along your nervous system, doing virtually no damage, and completely undetectable. You literally have NO symptoms.

It may be four days, it may be a year, but the camping trip is most likely long forgotten. Then one day your back starts to ache... Or maybe you get a slight headache?

At this point, you're already dead. There is no cure.

(The sole caveat to this is the Milwaukee Protocol, which leaves most patients dead anyway, and the survivors mentally disabled, and is seldom done).

There's no treatment. It has a 100% kill rate.

Absorb that. Not a single other virus on the planet has a 100% kill rate. Only rabies. And once you're symptomatic, it's over. You're dead.

So what does that look like?

Your headache turns into a fever, and a general feeling of being unwell. You're fidgety. Uncomfortable. And scared. As the virus that has taken its time getting into your brain finds a vast network of nerve endings, it begins to rapidly reproduce, starting at the base of your brain... Where your "pons" is located. This is the part of the brain that controls communication between the rest of the brain and body, as well as sleep cycles.

Next you become anxious. You still think you have only a mild fever, but suddenly you find yourself becoming scared, even horrified, and it doesn't occur to you that you don't know why. This is because the rabies is chewing up your amygdala.

As your cerebellum becomes hot with the virus, you begin to lose muscle coordination, and balance. You think maybe it's a good idea to go to the doctor now, but assuming a doctor is smart enough to even run the tests necessary in the few days you have left on the planet, odds are they'll only be able to tell your loved ones what you died of later.

You're twitchy, shaking, and scared. You have the normal fear of not knowing what's going on, but with the virus really fucking the amygdala this is amplified a hundred fold. It's around this time the hydrophobia starts.

You're horribly thirsty, you just want water. But you can't drink. Every time you do, your throat clamps shut and you vomit. This has become a legitimate, active fear of water. You're thirsty, but looking at a glass of water begins to make you gag, and shy back in fear. The contradiction is hard for your hot brain to see at this point. By now, the doctors will have to put you on IVs to keep you hydrated, but even that's futile. You were dead the second you had a headache.

You begin hearing things, or not hearing at all as your thalamus goes. You taste sounds, you see smells, everything starts feeling like the most horrifying acid trip anyone has ever been on. With your hippocampus long under attack, you're having trouble remembering things, especially family.

You're alone, hallucinating, thirsty, confused, and absolutely, undeniably terrified. Everything scares the literal shit out of you at this point. These strange people in lab coats. These strange people standing around your bed crying, who keep trying to get you "drink something" and crying. And it's only been about a week since that little headache that you've completely forgotten. Time means nothing to you anymore. Funny enough, you now know how the bat felt when he bit you.

Eventually, you slip into the "dumb rabies" phase. Your brain has started the process of shutting down. Too much of it has been turned to liquid virus. Your face droops. You drool. You're all but unaware of what's around you. A sudden noise or light might startle you, but for the most part, it's all you can do to just stare at the ground. You haven't really slept for about 72 hours.

Then you die. Always, you die.

And there's not one... fucking... thing... anyone can do for you.

Then there's the question of what to do with your corpse. I mean, sure, burying it is the right thing to do. But the fucking virus can survive in a corpse for years. You could kill every rabid animal on the planet today, and if two years from now, some moist, preserved, rotten hunk of used-to-be brain gets eaten by an animal, it starts all over.

So yeah, rabies scares the shit out of me. And it's fucking EVERYWHERE. (Source: Spent a lot of time working with rabies. Would still get my vaccinations if I could afford them.)

[u/TheMexicanJuan]

There is a girl that actually survived rabbies. But she had to be quickly put in an induced coma and basically shut her nervous system down for two weeks and they pumped her to the brim with antibiotics.

https://www.nbc26.com/news/local-news/jeanna-giese-16-years-later-surviving-rabies-to-build-a-beautiful-life

[u/adamtherealone]

So a bunch of bats were in our house last week, but they only came in once I was awake. They did not bite me, should I be worried

Update: I’m getting 11 shots today as the first dose

[u/kamehamehaa]

Rabies is literally one of the scariest ways to die I feel. If I ever had symptoms of rabies I would absolutely ask for some kind soul to off me gunshot to the head.

[u/LuangPrabangisinLaos]

A new a girl named Lyssa, she wasnt nice.