Library copies of bondage bestseller Fifty Shades of Grey have tested positive for herpes and cocaine.

Researchers from the Catholic University of Leuven made the shocking discovery after testing the ten most borrowed books at Belgium's Antwerp Library.

After a series of chemical tests, EL James' novel was revealed to be carrying traces of the herpes virus and A-class drug.

Jan Tytgat, a professor of toxicology, said the deposit on the books was too low to pose a threat to readers when leafing through the pages .

Pieter Asper's Tango was also found to be carrying herpes, while all ten tested positive for cocaine.

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

According to previous studies, highly sought-after library books like Fifty Shades have 25-40% more microbes on them than less-borrowed ones. One study, by a research team based in Utah, found bacterial colonies flourishing on the pages of library books.

Fifty Shades of Grey follows a young college student as she embarks on a sadomasochistic relationship with an older businessman, Christian Grey. It became the fastest-selling book of 2012 and has sold more than 70 million copies worldwide.

The movie, which will be directed by Sam Taylor-Johnson, is set to hit cinemas in the US in August 2014.

Jamie Dornan has been cast as S&M enthusiast Christian Grey and Dakota Johnson will play Anastasia Steele, his smart yet naive love interest.