A deadly, flu-based virus.
Causes a lethally high fever and is highly contagious.
So deadly because as the body fights off the disease,
it mutates into different strains of influenza,
making immunity next to impossible. Also called Superflu.

Ebola-like virus with first symptoms coughing
then quickly advancing to flu-like stage.

Disease responsible for turning many humans
into vampire-like creatures.

The brain cloud has no symptoms—
apart from quickly and painlessly killing in about six months.

An alien parasitoid macrovirus.
The adult aliens resemble deformed potato beings with legs,
while the younger aliens - nicknamed "shit-weasels" because they can
be created in a host organism's stomach and escape by eating their
host's body between the stomach and anus - are legless, smaller
versions of the adult alien.
Both adult and young aliens have a mouth consisting of a slit on the
underside of the head that goes down the length of the worm.
The lips separate to reveal hundreds of teeth that can bite through steel.

It causes all of the body's glands to be replaced with fatty tissue.

Victims bleed from their pores before eventually dying.
(See also Scarlet Plague.)

Victims bleed from their pores before eventually dying.
(See also The Red Death.)

A Martian disease, hallucinations are visible to others.
Curable only by euthanasia,
which is often performed as it is contagious.

A dangerous drug which is both a computer virus
capable of infecting the brains of unwary hackers in the Metaverse
and a mind-altering virus distributed by a network of Pentecostal
churches via its infrastructure and belief system.

A deadly disease of extraterrestrial origin
which causes rapid, fatal clotting of the blood.

A mysterious epidemic of sudden blindness
affecting virtually all humanity, leading to society's
collapse. So-called because victims see nothing
but a white glare.