At www.sciencedaily.com/releases/2012/11/121129093138.htm … a study of the bacterium that causes bubonic plague has revealed an older outbreak probably occurred in the first millennium AD. It was not a new disease, as supected by many people, pointing a finger at the devastating Plague of Justinian in the 6th century AD. This was a pandemic that decimated the Classical World and was the underlying factor behind the collapse of the Eastern Empire – and opened up the Levant and Egypt to Persian and Arab invasions.
At www.sciencedaily.com/releases/2012/12/121206121940.htm … it seems the Romany migrations may have an indirect link to the Plague of Justinian as genetic evidence indicates the migration began as early as 1500 years ago, with an origin, as expected, in NW India. This is speculation on my part but something must have set them in motion as they were never part of a violent or military expedition but just turned up on the edge of Europe after moving across the Russian steppe. According to a paper in Current Biology, December 6th, 2012, the genome of the Romany gypsies is mixed up with those of Europeans, as a result of admixture after they were washed up in Romania, Hungary and Slovakia etc. It confirms linguistic studies made a few years ago.