Theories have circulated about the nature of the "world's most mysterious manuscript." Some believe it is a pharmacopeia from medieval times used to keep track of early modern medicines. It also may have been a textbook for an alchemist, or, as other theorists believe, come from alien origin.
Havana syndrome is a bizarre set of medical symptoms experienced by the U.S. and Canadian embassy staff in Cuba between 2017 and 2018. Symptoms included hearing strange grating sounds, hearing and memory loss, nausea, and headaches. Studies of the affected diplomats revealed that all suffered some form of brain injury, but it was unclear or how or why this occurred.