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  • People have been scared of rabies for thousands of years, many times depicting their fear

  • in drawings and carvings of menacing dogs.

  • But rabies is scary for more reasons than just a painful bite.

  • Because once the virus is inside us, it not only destroys our body, but damages our mind,

  • and it can happen fast, or lay dormant for years before fatally attacking.

  • So how exactly do we get from a dog bite to a complete behavioral change to...death?

  • The virus that causes rabies is spread through saliva, so the most common way to contract

  • rabies is through an animal bite, most likely from a dog, bat, raccoon, skunk or fox.

  • There have been a few, rare cases of transmission through infected organ donors and an even

  • rarer instance of a lab accident, but for the most part it comes down to a bite from a rabid animal.

  • So even though it's a virus that can infect and kill humans, it's studied considerably in veterinary labs.

  • OK.

  • I am Dr. Susan Moore.

  • I'm the laboratory director of the rabies laboratory at Kansas State University, part

  • of the veterinary diagnostic lab within the vet school here.

  • We are the largest rabies serology laboratory in the world.

  • So the rabies virus is in the family lyssavirus,

  • lyssa means rage really.

  • So that kind of tells you what this group of viruses are capable of.

  • And what they're capable of is causing a very quick and painful death caused by the

  • virus making its way into your brain.

  • It's a neurotropic virus.

  • So that means it's preferentially going to infect neural tissue or neural cells.

  • So when it gets injected into the skin or the muscle, it's not going to replicate all

  • that well but all it needs to do is replicate enough that it can get to that neuromuscular

  • junction where that it can go from the muscle cells into the central nervous system.

  • Now, at this point you'd think your immune system would kick in, recognize this dangerous intruder and destroy it.

  • But, your immune system doesn't see it.

  • This is thought to be because the virus replicates slowly in the muscle tissue, slow enough not to cause any alarm.

  • This gives it a chance to reach the nervous system, where it hitches a ride up to the

  • brain and slips through the blood brain barrier.

  • It's behind this shield where the rabies virus can flourish while still being able

  • to hide from our immune system, because the blood brain barrier evolved to keep dangerous or harmful things out.

  • But sometimes that includes immune cells.

  • In fact, if T cells do get past the blood brain barrier, the rabies virus has evasion

  • techniques where it actually kills the T cells that are coming in.

  • As the virus replicates in the brain, it starts to mess with the brain's cellular proteins, causing neural dysfunction.

  • This is where certain symptoms of rabies start and how you can tell the infection has fully set in.

  • Once the infection has fully set in, it will start traveling back out through the nerves into innervated organs, hair follicles.

  • But again, particularly through to the salivary glands.

  • So that it could be transmitted out.

  • These neurological symptoms also help the virus transfer to a new host.

  • Hypersalivation ensures there is enough rabies-infected saliva in the optimal transmission location, your mouth.

  • And hydrophobia, or trouble swallowing, ensures that it stays there.

  • In animals, the aggression can result in an attack on another animal or a human.

  • Put all three of those together and you have a very effective way to ensure the rabies virus is passed on.

  • Saliva is the way that rabies is transmitted.

  • The way the virus is adapted, it is not in blood.

  • It's not in body fluids.

  • So it has to find a way to be transmitted effectively, right, to perpetuate its existence.

  • Now, this neurological damage caused by the infection is the thing that finally tips off the immune system.

  • However, at this point it's too late.

  • Even though your immune system is finally going after the virus, it has already spread throughout the body.

  • After that you have to remember this period is pretty short.

  • There's just a couple days because then it'll progress into a coma and then death which

  • is usually due to some kind of organ failure.

  • But a bite from a rabid animal doesn't always mean certain death.

  • People who have been exposed to the rabies virus can get a series of shots that can boost

  • the immune system and fight off the virus, you just need to get to it before it reaches the brain.

  • So surviving rabies is all about timing and the location where you get bit.

  • Where you get bit.

  • It plays a big role.

  • So since the virus has to travel through the nerve system, the closer, and get to the brain,

  • the closer that bite is to the brain, the better for the virus.

  • Bats are a danger for that reason that it's going to be biting probably around

  • your head or your hands. But also you don't notice a bat bite because the teeth are so small

  • and they are so small.

  • Maybe.

  • You have a bat on your shoulder and you don't know it.

  • You just looked on your shoulder, didn't you?

People have been scared of rabies for thousands of years, many times depicting their fear

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What Happens When a Human Gets Rabies?

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    Jerry Liu posted on 2019/08/01
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