<P> McCormick has suggested that earlier archaeologists were simply not interested in the "laborious" processes needed to discover rat remains . Walløe complains that all of these authors "take it for granted that Simond's infection model, black rat → rat flea → human, which was developed to explain the spread of plague in India, is the only way an epidemic of Yersinia pestis infection could spread", whilst pointing to several other possibilities . Similarly, Green has argued that greater attention is needed to the range of (especially non-commensal) animals that might be involved in the transmission of plague . </P> <P> A variety of alternatives to the Y. pestis have been put forward . Twigg suggested that the cause was a form of anthrax, and Norman Cantor thought it may have been a combination of anthrax and other pandemics . Scott and Duncan have argued that the pandemic was a form of infectious disease that they characterise as hemorrhagic plague similar to Ebola . Archaeologist Barney Sloane has argued that there is insufficient evidence of the extinction of a large number of rats in the archaeological record of the medieval waterfront in London and that the plague spread too quickly to support the thesis that the Y. pestis was spread from fleas on rats; he argues that transmission must have been person to person . This theory is supported by research in 2018 which suggested transmission was more likely by body lice and human fleas during the Second Pandemic . </P> <P> However, no single alternative solution has achieved widespread acceptance . Many scholars arguing for the Y. pestis as the major agent of the pandemic suggest that its extent and symptoms can be explained by a combination of bubonic plague with other diseases, including typhus, smallpox and respiratory infections . In addition to the bubonic infection, others point to additional septicemic (a type of "blood poisoning") and pneumonic (an airborne plague that attacks the lungs before the rest of the body) forms of the plague, which lengthen the duration of outbreaks throughout the seasons and help account for its high mortality rate and additional recorded symptoms . In 2014, scientists with Public Health England announced the results of an examination of 25 bodies exhumed from the Clerkenwell area of London, as well as of wills registered in London during the period, which supported the pneumonic hypothesis . </P> <P> There are no exact figures for the death toll; the rate varied widely by locality . In urban centres, the greater the population before the outbreak, the longer the duration of the period of abnormal mortality . It killed some 75 to 200 million people in Eurasia . According to medieval historian Philip Daileader in 2007: </P>

When did the black plague begin and end