Yahoo News explains: Russia’s the focus in diplomat attacks, but the cause remains a mystery

It’s been nearly two years since U.S. diplomats in Havana began to experience strange symptoms, such as dizziness, cognitive issues and problems with their hearing, vision and balance. This year, U.S. diplomats in Guangzhou, China, experienced similar symptoms. It was reported this week that U.S. intelligence agencies believe Russia may be behind the attacks, but haven’t formally accused the country. Yahoo News explains what the attackers could have used, and what researchers have learned about the illness.