Researcher Marc Buhler believes he has tracked down the source of a genetic marker shared by individuals with Jewish and Viking ancestral origins. The marker in question is a mutation that may be an inherited shield against AIDS. Buhler believes the genetic marker came to Scandinavia when Swedish Vikings visited the [northeastern area of the Black Sea] area between 800-1000 CE, and was distributed to Ashkenazi Jews when many of them left Germany after a 1350 bout of plague and traveled east, mingling with the Jews of the Khazar region. He says that a previous study indicated the incidence of this marker in about one in three Ashkenazi Jews and one in four Icelanders.
Iceland is one of my exact mtDNA genetic matches by autosomal STR analysis.
Original article is here.