This thread is simple: make your own disease, and the biggest, baddest, one wins. (Though their is no end to this thread....)

Corona!

You win. Unless someone can actually top that.

Whoooo! I finally win something!

The black death

These two are really scary!

Remember, you can make up your own too.

Idiotic Death:

You catch it from anybody, it is highly infectious, and it's symptoms make you the highlight of everyones jokes as everything that happens to you from now on is just silly.

Unless cured in seven days you slip on a banana peel and die

Cure: explain the sound of one hand clapping

*slip*

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaaaaaaaaaaaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhh.............

*thud*

The Immortality disease

You are immortal, You will witness the rise and fall of empires, you will experience the death of those you hold most dear to you, you cannot join them, you can never die. Truly a fate worse than death...

No it isn't contagious, no there is no cure. How do you catch it? It just suddenly happens...

That is actually a disease I'm in the process of making a character for

Nice! 

How about Terran Malady: 30 days to be cured or become a petrified statue with no cure. As you harden, you get a little bit of good stuff, but mostly bad stuff.

Whether you are an earth genasi or not

a diesese that slowly burns with fire from the inside out mildly contagious kills in 1 month cure does exist but the side effects are irreversable and can be deadly in the long term 

what happened?

spam sickness: everything you say is either spam (see above) or Spam

Quote from Nikoli_Goodfellow_King_Of_Random >>

Idiotic Death:

You catch it from anybody, it is highly infectious, and it's symptoms make you the highlight of everyones jokes as everything that happens to you from now on is just silly.

Unless cured in seven days you slip on a banana peel and die

Cure: explain the sound of one hand clapping

 me snaps ah ha ive done it 

The Dark Pestilence:

It comes in the form of a dark cloud on the horizon, entwined with streaks of rainbow hues. The cloud races quickly, faster than the wind, bearing down upon everything before it. A single touch of the ashen smog from this plague ensures your demise as the disease spreads through out your body, ultimately turning you into an Ash Golem, forced to watch through its cruel eyes for all of eternity. And should you get caught in the open, and get hit by the dark storm full-on, your transformation will be swift and painful.

The only known way to save a victim of the Dark Pestilence is to cut of the infected limb. A fully infected creature cannot be reverted back to their humanoid form by any means, and their soul remains trapped in the Ash Golem's body, even if the golem is destroyed.

Nero plague "the endless death"

At first the bacteria takes root on the lunges, causing coughing, sneezing, and trouble breathing. The coughing and sneezing make it very infectious. This lasts for a few weeks. After the that, it spreads to your blood stream, and dies in you lunges, so, for a few days, to are without symptoms, so you think you are healthy again. While in your blood, it can be spread through blood to blood contact. From the blood stream, but it spreads to the brain. While in the brain, it destroys brain cells, causing memory loss, and increasing levels of insanity, until it destroys a vital part of the brain, causing death a slow, painful, gruesome death.

And to make things worse, it's immune to antibiotics and bacteria phages.

Quote from Tom_The_Gelatinous_Cube >>

The black death

 I have to say, I think this wins. Most people do not know how terrible the black death was.