Das tödlichste Virus der Welt

Monsters really exist. But outside of our imagination, they really don't mean us any
harm. Evolutionarily,
they can only survive by invading our bodies
and bypassing our defenses. For us this often ends fatally, but they have
no bad intentions. One of the most dangerous of these
monsters is the Rabies lyssavirus. Or the rabies virus. Once you show symptoms
of contagion, your death is almost certain. It is named after Lyssa, the ancient Greek goddess
of madness.

And has been haunting us
for at least 4,000 years. Lyssa turns animals
into bloodthirsty monsters. And humans into hydrophobic zombies. But what makes Lyssa so intriguing is not only how grotesque and deadly infection
with the virus is, but also how incredibly good
it is at evading our defenses. (Happy Music) Viruses exist
somewhere between life and death. Little more than a few
genetic instructions that
can only reproduce with the help of living cells. Lyssa is simple, even for a virus

It consists of only five genes, i.e.
building instructions for five proteins, with which it masters quite difficult
challenges. Infect a mammal,
bypass its immune system, travel to the brain,
multiply, and infect new hosts. Let's look at
what happens when you get infected. It starts with a bite,
often from a dog, that has millions of viruses in its saliva,
pushing them deep into your tissues. Your goal, your nerve cells,
the neurons.

These are essentially living
electrochemical cables that carry signals throughout your
body. They are up to 1.5 meters long with
all the cell machinery at one end and
an interface at the other.
The cells can communicate with each other via the interface. By
passing on chemical substances there and thus transferring information. Lyssa probably docks onto
the receptors required for this and thus gets
into the unsuspecting nerve cells. Once inside there
is a big problem. The virus needs to get to the machinery
at the other end. To occupy the cell
and multiply. However, because neurons
are often quite long, this can be a very long way. However, there is
a practical solution. Inside,
so-called microtubules support the cell and give it
structural stability. Additionally, they serve as rails for a specialized
transportation system.

These are actually
biological engines that consume energy
and deliver packages. They consist
of 50 different proteins. Ten times as many as the virus. And look
like a little pair of shoes. Using one of his five proteins, Lyssa can
hijack this amazing system and command
it to be transported to the core. And what does the immune system do
to prevent all of this? Well, unfortunately not very much. During a virus attack, your civilian cells are also
extremely important to summon your immune soldiers
. The civilians realize
that they have been infected and then release hundreds of thousands of
proteins of a special kind called interferons,
which spark the viruses.

We're going to have to over-
simplify this, but in short,
interferons alert your immune system to make anti-viral weapons. But they do even more. They instruct the civilian cells to
temporarily shut down their protein production. As a result, the viruses can no longer
multiply efficiently. Interferons
also instruct the cells to become quasi-transparent. This is important, otherwise
an immune cell has no chance of noticing that a civilian cell
has been infected.

Because the viruses
can hide in it. So your body helps the immune cells
to detect the viruses. By creating a kind of window
into the cell interior, so-called MHC class I molecules. Cells are constantly making
stuff to stay alive. In order to show your immune cells
what is going on inside them, they take random samples
from their production and place them in tiny shop windows,
thus enabling an insight. Interferons cause the cells
to build in many more such windows. Which makes them almost
transparent. If a cell is infected and is
forced to make parts of the virus, the immune cells notice
these parts through the window and order the cell to
kill itself.

And with it
all the viruses in it. This is one of the most effective
methods against virus attack. Unfortunately, however, Lyssa prevents
the neurons from making interferons. And thus remains undetected
behind the cell wall. Also, unlike many other viruses,
it does not kill its host cell when it multiplies. Which would also trigger the alarm
. Instead, it steals
from neuron to neuron. And slowly getting
to your brain. This phase can last weeks or months,
very rarely even years. Depends on various things,
such as whether you were bitten on the face or foot. And how many viruses
got into your muscles. Lyssa is a patient monster
and will keep at it until it reaches its target: your brainstem.
(Easy music) Now the immune system finally realizes
that something is wrong and reacts. It unleashes some of your
most powerful anti-viral cells, the T-killer cells. You should find the infected cells
and wipe out the enemy. For other viral infections,
this would now be the turning point.

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