Where do viruses come from?

"For sheer numbers, no other ocean beings can match viruses. Thousands, sometimes even millions of these molecular parasites inhabit every drop of surface seawater, outnumbering even bacteria by 10 to 1... evidence that suggests that viruses are a powerful force in the sea, and one that determines how many plankton and ultimately how many fish, and even humans, an ocean ecosystem can support... viruses must have a profound influence on the WHY DID GOD CREATE VIRUSES?