Last December, Peter Stäheli and his team at the University of Freiburg, Germany,
reported that most of the human isolates found so far were most closely related to the
strains used in the
labs that had found them — suggesting the findings had been artifacts, caused by contamination.
Of note, Dr. Warden's
lab reports that, at least once during backcrossing, a heterozygous female was bred to a C57BL / 6J inbred male (thus the Y chromosome of the congenic
strain is of C57BL / 6J origin).