Tales from the Blind Pig (TBP)
In the year 2001, a NASA spacecraft named Beagle II returned from the planet Mars with soil samples. Unfortunately, it also carried a microscopic hitchhiker, a pathogen which came to be known as the Martian Flu Virus. Even less fortunately, Beagle II crashed, thus neatly evading NASA's biological quarantine procedures and releasing an extraterrestrial virus on an unsuspecting world. The 'Flu quickly spread across the entire planet, resulting in an overall death rate of approximately 25% (somewhat lower in First World nations, somewhat higher in the Third World).
As if the lethal pandemic itself wasn't enough, the Martian Flu Virus had a nasty trick up its sleeve: A complication which became known as Stein's Chronic Accelerated Bio-morphic Syndrome, SCABS for short, the first confirmed case of which was observed on 19 April 2002. SCABS occurs in about 8% of all 'Flu victims, and it typically shows up anywhere from 6-12 months after the initial 'Flu infection. "SCAB" is a common term for those afflicted with SCABS. The roughly 67% of 'Flu victims who neither die nor come down with SCABS, end up suffering cold/flu symptoms of some degree of severity, with no lingering after-effects.
Martian Flu is an extremely mysterious disease. There is no known cure, nor does anyone know how it's transmitted to its victims. The good news is, those who survive their initial bout with Martian Flu are forevermore immune to it.
In essence, SCABS takes your DNA and scrambles it up real good. Presumably, all 'Flu victims have some degree of genetic alteration -- it's just that only in those who die or come down with SCABS is it significant enough to make any difference. There are a few distinct varieties of SCABS, and it's possible to have two or more varieties simultaneously. There are animorphs, i.e. human/X hybrids, where "X" is "any lifeform besides human"; chronomorphs, whose biological aging occurs differently from the standard 1-second-per-second rate; gendermorphs, people with SCABS-altered sex; polymorphs, true shapeshifters; and inanimorphs, who have transcended the limits of biological existence.
Most stories in this setting focus on the doings of the regular customers of a SCAB-friendly bar called the Blind Pig Gin Mill (hence, the name of the setting). However, it is certainly possible to look in on other parts of the 'Flu-altered world, which some writers have done to good effect. If you'd like to read more TBP stories, you'll find a good selection at the Transformation Stories Archive.
This story universe was created by Mark Van Sciver in 1996. It is open to all comers. Mr. Van Sciver has declined to act as arbiter for TBP stories; instead, Bryan Derksen and a couple others rule on whether or not any given concept or story is canonical for TBP.