"Havana syndrome" is back in the spotlight again after Austria and the United States announced that they were investigating reports that American diplomats and other officials in Vienna had health problems similar to the mysterious syndrome.
US senators reported in May that the government was investigating an apparent increase in mysterious directed energy attacks, amid new reports of possible brain-damaging incidents in the United States.
The mysterious attacks have sickened US diplomats and intelligence agents with diseases and sometimes brain damage in Cuba, China, Russia and other countries.
Havana Syndrome is a group of medical signs and symptoms reported by US and Canadian embassy staff in Cuba that dates back to late 2016 as well as later in some other countries, including the United States.
Moscow is suspected of being behind this, even if the mechanism for those attacks has not yet been clarified.
There are more than 130 reports of people suffering from "Havana syndrome" around the world over the past five years, according to the American newspaper, "The New York Times".