The Creature from Beyond Infinity by Henry Kuttner

Like a great, lethal snake, plague creeps through the galaxies. No conscious entity can halt its progress, and life is slowly draining from planet after planet. Only one super-intelligence is capable of preventing cataclysm. To do it, he must penetrate far beyond infinity--to the formless, deathless creature out to kill the universe. A pulp novella that can stand right next to any other Sword and Spaceship tale from the era. In this story, there are two co-running plots of an alien searching for human geniuses throughout time and one of those geniuses striving to contain a pandemic that is turning people into life force vampires. With muscle and brain-bound men, strong-willed beauties helpless in the arms of strong men, and lots of action.