Library copies of "Fifty Shades of Grey" tested positive for traces of the herpes virus and cocaine, according to two Belgian professors.

Researchers from the Catholic University of Leuven ran bacteriology and toxicology tests on the 10 most borrowed books at the Antwerp library and recently revealed their findings.

E L James' bestselling erotica series wasn’t the only "viral" book on the shelves. A romance by Pieter Aspe titled "Tango" also tested positive for herpes.

However, researchers say concentrations of the virus on the books were so minimal that it would be impossible to contract herpes by touching the pages.

And although all 10 of the most popular books tested positive for trace amounts of cocaine, researcher Jan Tytgat says there’s nothing to worry about.

"The levels found won't have a pharmacological effect. Your consciousness or behavior won't change as a result of reading the tomes," he told the Flanders News.

This isn’t the first time scientists have tested book covers.

A 2011, Brigham University study found that books in the school library categorized as "high demand" averaged 25 percent to 40 percent more microbial life than other books.

Still, research shows it's more important to wash your hands after touching a library door than a paperback. Books consistently harbor far less bacteria than doorknobs.

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Laura Moss writes about a variety of topics with a focus on animals, science, language and culture. But she mostly writes about cats.

'Fifty Shades of Grey' goes viral -- and not in a good way
Researchers run bacteriology and toxicology tests on popular library books and find traces of cocaine and the herpes virus.