Researchers at McMaster University, analyzing thousands of documents covering a 300-year interval of the plague outbreak in London, England, estimate that the disease spreads four times faster in the 17th century than in the 14th century.
The conclusion, published today (October 19, 2020) Proceedings of the National Academy of Science, Showing a striking acceleration in plague transmission between the Black Death of 1348, estimated to be more than a third of Europe’s population, and the subsequent epidemic, which ended in the Great Plague of 1665.
Researchers found that in the 14th century, the number of people infected during the outbreak almost doubled every 43 days. By the 17th century, the number was doubling every 11 days.
“It’s a surprising difference in how fast the plague epidemic grew,” says David Arka, a professor in the Department of Mathematics and Statistics and investigator at McMaster with the Michael G. DeGroote Institute for Infectious Disease Research, the study’s lead author Huh. .
Earn and a team comprising statisticians, biologists and evolutionary geneticists estimated mortality by analyzing historical, demographic and epidemiological data from three sources: the individual testamentary and testator, the parish register, and the London Bill of Mortality.
It was not just a matter of counting the dead, as there is no published record of deaths in London before 1538. Instead, researchers established information from individual testamentaries and examiners to establish how the plague was spreading through the population.
“At the time, people generally wrote a will because they were dying or they feared they might die imminently, so we speculated that Wills’ dates would be a good proxy for the spread of fear, and of themselves Death. For the 17th century, when both bequests and mortality were recorded, we compared what we could get from each source, and we got similar growth rates, “earn.” 14th or 17. Nobody living in London in the 20th century had imagined how these records could be used hundreds of years later to understand the spread of the disease. ”
While previous genetic studies have identified Yersinia pestis as the pathogen that causes plague, very few people know how the disease was transmitted.
“From genetic evidence, we have good reason to believe that the strain of the bacteria responsible for the plague has diminished greatly over this time period, so this is a fascinating result,” says Hendrik Poiner, a professor in McMaster’s anthropology department , Who is also affiliated with the Michael G. DeGroote Institute for Infectious Disease Research, and is a co-author on the study.
The estimated speed of these epidemics, along with other information about the biology of the plague, suggests that during these centuries the plague bacterium did not spread primarily through human-to-human contact, known as pneumonic transmission. Was known in Growth rates for both early and later epidemics are more consistent with the bubonic plague, which is spread by the bite of infected fleas.
Researchers believe that population density, living conditions, and cooler temperatures can potentially explain acceleration, and that historical plague epidemics provide lessons for understanding transmission patterns COVID-19 And other modern epidemics.
This new digitized archive developed by Ear’s group provides a way to analyze epidemiological patterns from the past and has the potential to lead to new discoveries about infectious diseases, and the factors that drive their spread, over time. Have changed with.
Reference: 19 October 2020, Proceedings of the National Academy of Science.
DOI: 10.1073 / pnas.2004904117