Note: The idea was inspired by the Dead Rising video game. Just in case you see the similarities.
Deep within the Nirvana desert, secret tests were underway, far below the surface in a biological weapons facility. They had altered a species of Hornets, making them parasitic, and able to burrow into a hosts body, tapping into they're spinal cord and hijacking they're nervous systems. It was intended as a way of clearing out enemies that had fortified themselves. Swarming into the enemies strong hold, they could take control of any hostiles and use the Hornets influence turn them against each other, or to sabotage for them. This was achieved by a "Queen" a human implanted with a Queen Hornet. The two would merge, the Queen symbiotic and allowing the Host to take direct control over the Hornets. Any bunkered down enemies would be easily over come and befriend any force bearing a Queen. It was a new and revolutionary way of war, but those that knew of its research, it was considered the worst, most diabolical weapon in development since the Atom Bomb.
One of the few men who had successfully become a Queen had sabotaged the project. The Queen inside him was able to communicate with him through his own mind, and slowly began to manipulate him. Now a puppet to the Queen, he freed the Hornets, and they assisted him in infecting the facility.
All previous test subjects had been slow, dumb creatures, but these were a new breed of Hornet Hosts. They had retained their human intelligence and will power, and had became stronger, rather then weaker. These new Hosts took up arms, and under the Ruler's command, they over powered the local military settlements, leaping across great distances and killing men with their bare hands when needed. Though they could be brought down with enough punishment from gun fire, the Base fell.
Choppers were loaded and sent to nearby major cities. Each crash landed in the streets, and emerging from them were twisted, bloated monstrosities. Their skin vibrated with the excited thrilling of thousands of Hornets, burrowed deep in their hosts body. The Hosts would clamber out of the wreckage and burst, sending the Hornets forth to claim the populace.
The infection spread, and soon, that entire corner of America was Hornet controlled. As fierce and as organized as the Hornets were, the Ruler bided his time. They would be destroyed if they pushed further. The united forces of the world would prove too powerful.
Years went by. The Hornets would nip at the borders of their territory, and the humans would fight back. There was no definitive winner here, and another city was lost as often as it had been saved. The humans developed gases that could kill the parasite, and it gave them an extra edge over the invaders.
The game begins with the characters living they're lives in the city of Brooker. The city was always in danger of an attack, but the military presence there was enough to give closure to its inhabitants.
The Hornets have had time. New breeds have emerged, and it is only a matter of time before they step forward for a push into human lands. Each life taken will add to their ranks, and Brooker will be among the first wave of attacks. Can you survive? Or will you become a host, an incredibly strong and fast killer?