section_path: 14th-century plague/Causes/Alternative explanations
section_name: Alternative explanations
paragraph_text: Alternative explanations
  
  Researchers are hampered by a lack of reliable statistics from this period. Most work has been done on the spread of the disease in England, where estimates of overall population at the start of the plague vary by over 100%, as no census was undertaken in England between the time of publication of the Domesday Book of 1086 and the poll tax of the year 1377. Estimates of plague victims are usually extrapolated from figures for the clergy.
  
  Mathematical modelling is used to match the spreading patterns and the means of transmission. In 2018 researchers suggested an alternative model in which "the disease was spread from human fleas and body lice to other people". The second model claims to better fit the trends of the plague's death toll, as the rat-flea-human hypothesis would have produced a delayed but very high spike in deaths, contradicting historical death data.
  
  Lars Walløe argued that 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". Similarly, Monica 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.
  
  Archaeologist Barney Sloane has argued that there is insufficient evidence of the extinction of numerous rats in the archaeological record of the medieval waterfront in London, and that the disease spread too quickly to support the thesis that 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 fleas during the second plague pandemic.