The Slender Sickness

There's a peculiar illness going around many countries, believed to originate somewhere in Germany. It's a virus that has been worrying many people all over the world.
Symptoms are as follows:

Vomiting.
Sleep Deprivation.
Intense Paranoia.
And extreme hallucinations.

There are various reports of people mysteriously disappearing only a few weeks after infection. And many people affected by this disease report seeing a tall, pale-skinned man donning a black suit and tie. Hundreds, thousands of people seeing the exact same entity wherever they go.
It's always watching. With no eyes. And they call him "Thę̥͓ͅ Sle̛̞̤͕͔͕̦n̬͍͎͖͍͟d̷̙̹̣er M̶̲̯̬̞͕̫a̘̹̝̯ṋ̫̭."