This item on the website for San Diego State University describes a virus discovered by SDSU researchers that's found in something like half the people on the planet.
The virus, given a name for which nine-year-old boys everywhere on the planet are sending up hosannas of thanks, is called "crAssphage." Yes, the capital letter is part of the name.
It inhabits bacteria that live in the human digestive system which are called bacteriodetes. Those bacteria live near the end of the intestines (if you don't stop snickering I'm going to send you to the principal's office) and scientists think they may play a role in affecting digestion in a manner which in turn can have an impact on obesity.
What originally drew my attention to the article was the headline the SDSU website gave it: "Novel Virus Discovered in Half the World's Population." The headline writer obviously intended to describe the virus as newly-found when he or she used the word "novel," but of course that word also denotes book-length fiction.
And since a virus is a biological agent that is capable only of reproducing itself using DNA from host material, I think the SDSU headline writer has also hit upon an explanation for a sizable majority of the crap that's on bookshelves and the New York Times bestseller lists. More than half of humanity is afflicted with a virus that causes it to believe it can produce a novel, only most of them are just reproductions of something someone else already did.