The Ebola virus that has killed scores of people in Guinea this year is a new strain — evidence that the disease did not spread there from outbreaks in some other African nations, scientists report. "The source of the virus is still not known," but it was not imported from nearby countries, said Dr. Stephan Gunther of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany. He led an international team of researchers who studied the genetics of the virus and reported results online Wednesday in the New England Journal of Medicine.