“Bubonic plague outbreaks spread four times faster in the 17th century than 14th century, study suggests - The Independent” plus 1 more

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Bubonic plague outbreaks spread four times faster in the 17th century than 14th century, study suggests - The Independent Posted: 20 Oct 2020 09:53 AM PDT Researchers examining the impacts of bubonic plague in London, since it first arrived from Asia in the mid 1300s, until the last major epidemic in 1666, have estimated the disease spread four times faster in the 17th century than it had in the 14th century. After analysing thousands of documents covering a 300-year time span detailing the plague outbreaks in the capital, researchers from McMaster University in Canada have revealed how the spread of the disease accelerated during later epidemics. Later known as the Black Death, the plague, caused by the Yersinia pestis bacteria and transmitted by fleas on black rats, arrived in England in June 1348. It reached London by the autumn, and covered the whole country by summer 1349. That epidemic is estimated to have killed between 40-60 per cent of the population of England and more than one-third of the population of Europe. In England it died down by December 1349, but remained endemic over the next three centuries, occasionally flaring up. The last major epidemic was the Great Plague of 1665 in London. In that outbreak an estimated 100,000 people, almost a quarter of London's population, died in 18 months. Read more The research team found that in the 14th century, the number of people infected during an outbreak doubled approximately every 43 days. But by the 17th century, the number of infections was doubling every 11 days. "It is an astounding difference in how fast plague epidemics grew," said David Earn, a professor in the Department of Mathematics & Statistics at McMaster University and investigator with the Michael G DeGroote Institute for Infectious Disease Research, who is lead author on the study. Professor Earn and a team including statisticians, biologists and evolutionary geneticists estimated death rates in London by analysing historical, demographic and epidemiological data from three sources: personal wills and testaments, parish registers, and the London Bills of Mortality. It was not simply a matter of counting up the dead, since no published records of deaths are available for London prior to 1538. Instead, the researchers scoured written records for information, even using individual wills and testaments to establish how the plague was spreading through the population. "At that time, people typically wrote wills because they were dying or they feared they might die imminently, so we hypothesised that the dates of wills would be a good proxy for the spread of fear, and of death itself. "For the 17th century, when both wills and mortality were recorded, we compared what we can infer from each source, and we found the same growth rates," said Professor Earn. "No one living in London in the 14th or 17th century could have imagined how these records might be used hundreds of years later to understand the spread of disease." While previous genetic studies have identified Yersinia pestis as the pathogen which causes plague, little is known about how the disease was transmitted. "From genetic evidence, we have good reason to believe that the strains of bacterium responsible for plague changed very little over this time period, so this is a fascinating result," says Hendrik Poinar, a professor in the Department of Anthropology at McMaster, 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 plague, suggest that during these centuries the plague bacterium did not spread primarily through human-to-human contact, known as pneumonic (relating to the lungs) transmission. Growth rates for both the early and late epidemics are more consistent with bubonic plague, which is transmitted by the bites of infected fleas. Researchers believe that population density, living conditions and cooler temperatures could potentially explain the acceleration, and that the transmission patterns of historical plague epidemics offer lessons for understanding Covid-19 and other modern pandemics. The researchers said the new digitised archive developed over the course of the study provides a new way to analyse epidemiological patterns from the past and has the potential to lead to new discoveries about how infectious diseases, and the factors that drive their spread, have changed through time. The research is published in the Proceedings of the National Academy of Sciences.

Study: Medieval plague outbreak exploded over 300 years - Missoula Current Posted: 20 Oct 2020 08:11 AM PDT The East Smithfield cemetery, located in London, built in 1348. (Credit: Museum of London Archeology) (CN) — A study released Monday has found that over the course of 300 years, plague outbreaks in London dramatically picked up speed and spread up to four times faster in the 17th century than at their emergence in the 14th century. Details of the study are published in the journal Proceedings of the National Academy of Sciences, where researchers from McMaster University in Canada discuss this concerning series of events which could potentially hold important guidance about our future. The bubonic plague first arrived in Europe in 1347, carried by sailors on a trading ship from Asia. Over the next five years, the disease had claimed over 20 million European lives — over one-third of the continent's entire population at the time. Although the Black Death had officially ended by the early 1350s, the plague never went away and continued to reappear for the next few centuries. The most notable recurrence of this was the Great Plague of 1665, where a horrific outbreak in London was responsible for about 1,000 deaths a week, reaching its peak when a tragic 7,165 people were lost in a single week. The researchers combed through thousands of documents related to the medieval disease, including personal recountings, church records and the London Bills of Mortality. From these sources, the team of statisticians, biologists, and evolutionary geneticists approximated the loss of life, and found a chilling statistic: The infection rate in the 14th century doubled every estimated 43 days, but later in the 17th century, that rate had increased to doubling every 11 days. "It is an astounding difference in how fast plague epidemics grew," said lead author David Earn, a professor in the department of mathematics & statistics at McMaster. The authors note that it was an especially challenging task to estimate the death rate in London from the beginning of the outbreaks in the 1300s to the peak in 1665, as no official death records exist from before 1538. In an attempt to gain a more rounded picture of how rapidly the disease spread, they looked to examine individuals' wills and testaments. "At that time, people typically wrote wills because they were dying or they feared they might die imminently, so we hypothesized that the dates of wills would be a good proxy for the spread of fear, and of death itself," Earn said. "For the 17th century, when both wills and mortality were recorded, we compared what we can infer from each source, and we found the same growth rates." He added, "No one living in London in the 14th or 17th century could have imagined how these records might be used hundreds of years later to understand the spread of disease." The plague has been found to be associated with exposure to a bacteria called Yersina pestis, which travels through the air and through the bites of carriers like fleas and rats. Although these pests are said to be the cause of the rapid spread onboard ships, which carried the illness from port to port across Europe, scientists are still unclear about exactly how the disease spread. A photo of the one of the London Bills of Mortality, for the week beginning Sept. 26, 1665. (Photo by Clair Lees) "From genetic evidence, we have good reason to believe that the strains of bacterium responsible for plague changed very little over this time period, so this is a fascinating result," said co-author Hendrik Poinar, an anthropology professor at McMaster. Based on what researchers know about the epidemics and the gathered information from this study, they do not think it is likely that the pathogen's primary mode of transmission was from person-to-person spread. They suspect that, given the accelerated growth rates, infected fleas probably played a large role. The authors also emphasize that this research holds important lessons for society today as we face the effects of Covid-19. Looking at the trends from past epidemics, they believe that population density, living conditions, and cooler temperatures are all factors in facilitating the spread of disease. Some of these factors can already be seen taking effect throughout communities today, as Covid-19 disproportionally affects minority groups, highly populated regions, those with less access to health care, communities affected by climate change and more. In hopes that their work can provide some insight moving forward, Earn and his team have developed a digital archive capable of analyzing infection patterns across outbreaks of the past, and identifying significant changes over time.

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