<P> The results of the Haensch study have since been confirmed and amended . Based on genetic evidence derived from Black Death victims in the East Smithfield burial site in England, Schuenemann et al. concluded in 2011 "that the Black Death in medieval Europe was caused by a variant of Y. pestis that may no longer exist ." A study published in Nature in October 2011 sequenced the genome of Y. pestis from plague victims and indicated that the strain that caused the Black Death is ancestral to most modern strains of the disease . </P> <P> DNA taken from 25 skeletons from the 14th century found in London have shown the plague is a strain of Y. pestis that is almost identical to that which hit Madagascar in 2013 . </P> <P> The plague theory was first significantly challenged by the work of British bacteriologist J.F.D. Shrewsbury in 1970, who noted that the reported rates of mortality in rural areas during the 14th - century pandemic were inconsistent with the modern bubonic plague, leading him to conclude that contemporary accounts were exaggerations . In 1984 zoologist Graham Twigg produced the first major work to challenge the bubonic plague theory directly, and his doubts about the identity of the Black Death have been taken up by a number of authors, including Samuel K. Cohn, Jr. (2002 and 2013), David Herlihy (1997), and Susan Scott and Christopher Duncan (2001). </P> <P> It is recognised that an epidemiological account of the plague is as important as an identification of symptoms, but researchers are hampered by the lack of reliable statistics from this period . Most work has been done on the spread of the plague in England, and even estimates of overall population at the start vary by over 100% as no census was undertaken between the time of publication of the Domesday Book and the year 1377 . Estimates of plague victims are usually extrapolated from figures from the clergy . </P>

Where did the black death start and end