Dan Abnett
Pestilence
Eisenhorn (series)
An Imperial medicae investigates a deadly plague that is striking down the defenders of the Genovingian sector, and finds himself inveigled in a plot by the Ruinous Powers.
Warhammer 40k
short

Also in:
Deathwing
The Magos
There Is Only War
Lord of the Dark Millennium
Let the Galaxy Burn
25 For 25