Who is Cryptosporidium in destroy all humans?

In the context of the game or narrative "Destroy All Humans," who exactly is Cryptosporidium? Is it a main antagonist, a side character, or perhaps a mysterious force that drives the plot? Its name suggests a parasitic or viral entity, but what role does it play in the overall story? Does it possess unique abilities that threaten the human population? Or is it simply a symbolic representation of a larger threat? Clarifying Cryptosporidium's identity and role within the narrative would greatly enhance my understanding of the game's storyline and themes.