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Time of India
3 days ago
- Health
- Time of India
Plague became less deadly to last longer, study finds
Paris: The bacteria that cause the plague evolved to become less deadly over time, allowing it to continue infecting people in three separate pandemics over more than a thousand years, new research said Thursday. The first pandemic -- the plague of Justinian -- struck in the 500s at the start of the Middle Ages and lasted for around 200 years. The Black Death began in the mid-1300s and would become the deadliest pandemic in human history, killing up to half of the people in Europe, western Asia and Africa, with outbreaks continuing for centuries. The third bubonic plague pandemic broke out in China in the 1850s and continues today, with some cases still being recorded in parts of sub-Saharan Africa. "The plague bacteria have a particular importance in the history of humanity, so it's important to know how these outbreaks spread," said Javier Pizarro-Cerda, a microbiologist at France's Pasteur Institute and co-author of the study published in the journal Science on Thursday. The researchers examined samples of Yersinia pestis , the bacteria that cause the plague, dating back to each pandemic. In all three cases, the genes of each plague bacteria evolved to become less virulent and less deadly over time, according to the study. By causing less severe infections, the bacteria are thought to have extended the length of the pandemics because it gained more opportunities to spread between people. The researchers confirmed this theory by infecting rats with recent plague samples, showing that the disease lasted longer when the virulence decreased. While antibiotics can now effectively fight off the plague, the research could shine a light on how other pandemics might evolve. "This allows us to gain a comprehensive understanding of how pathogens can adapt to different situations," Pizarro-Cerda said. "We finally better understand what the plague is -- and how we can develop measures to defend ourselves," he added.
Yahoo
3 days ago
- General
- Yahoo
Single gene may help explain the plague's persistence throughout human history
When you buy through links on our articles, Future and its syndication partners may earn a commission. Scientists have discovered how adaptations in a single gene helped the plague survive for hundreds of years. Responsible for the deadliest pandemic in history, the bacterium that causes the plague, Yersinia pestis, has existed in varying strains from ancient times until today. Now, scientists have unearthed a genetic clue as to how the infamous disease has persisted for millennia, with devastating outbreaks smoldering across centuries. They published their findings Thursday (May 29) in the journal Science. "This is one of the first research studies to directly examine changes in an ancient pathogen, one we still see today, in an attempt to understand what drives the virulence [disease severity], persistence and/or eventual extinction of pandemics," study co-senior author Hendrik Poinar, director of the Ancient DNA Centre at McMaster University in Ontario, Canada, said in a statement. Y. pestis has been infecting humans since before recorded history began. The most common form of the disease is known as "bubonic" and most often enters the body through bites from infected fleas, although people can less commonly catch it directly from infected animals, including rats and cats. Once inside the body, the bacterium travels to the lymph nodes and replicates. As it multiplies, it triggers the formation of painful, pus-filled "buboes," for which the bubonic plague is named. The plague bacterium can also cause a blood infection, called septicemic plague, and lung infection called pneumonic plague. Related: Oregon's 1st bubonic plague case in 8 years tied to patient's pet cat The three major plague pandemics are among the deadliest outbreaks in human history. The first pandemic, the Justinian Plague (which occurred roughly between A.D. 542 and 750), slashed the population in parts of the Mediterranean to by an estimated 40% by the end of the sixth century. The second, and most infamous, outbreak of the disease was the 14th-century Black Death that ravaged Europe and the Middle East. The single deadliest pandemic in recorded history, the Black Death killed approximately 25 million people in Europe alone — between 33% and 50% of its population. A third, lesser-known global plague pandemic began in 1855 in China's Yunnan province and killed more than 12 million people in India and China alone. This pandemic was considered active until 1960, after which plague deaths dropped to lower levels. Plague epidemics continue to this day, with the Democratic Republic of the Congo, Madagascar and Peru being the most endemic countries, according to the World Health Organization. Besides the staggering death counts associated with the pathogen, what's perhaps most remarkable about Y. pestis is the longevity of its strains. Strains of the Justinian Plague bacterium took 300 years to go extinct after outbreaks were first recorded, and one of the two lineages from the Black Death re-emerged in waves for 500 years before its disappearance, while the other became the ancestor of all present-day strains. To investigate the genetic toolkit Y. pestis uses to persist for so long, researchers conducted an analysis of a plague gene known as pla across hundreds of samples collected from ancient and modern victims of the disease. The pla gene codes for an enzyme that helps Y. pestis move through the body undetected by the host's immune system. Previous studies have suggested that pla is a key factor that modulates both the lethality of a given plague strain and its ability to spark outbreaks in humans. However, one plague strain can carry a different number of pla genes than the next, and it wasn't clear how this copy number might impact their biology, the researchers noted. To investigate, they collected multiple modern strains of Y. pestis from Vietnam that had varying numbers of copies of pla inside their genomes; carrying more copies of the gene means that the bacteria can crank out more copies of the enzyme. After injecting these different plague strains into mice, they found that the strains with fewer copies of pla led to longer infections but reduced the disease's mortality rate by up to 20%. RELATED STORIES —Diagnostic dilemma: A scientist caught plague from bacteria thought to be 'noninfectious' —Could bacteria or viruses lurking in ancient Egyptian mummies unleash a plague today? —'Black death' survivors had plague-resistant genes that may boost their descendants' risk of autoimmune disease Across the ancient plague genomes they analyzed — 20 of which dated to the first plague pandemic and 94 of which were from the second — the researchers noted a pattern where the plague strains lost copies of pla over time, namely in later stages of each pandemic. Among the modern genomes, they found three strains that hint that the same pattern is unfolding today. They theorized this adaptation likely made infections less virulent, or harmful to the host's body, over time. This suggests that the evolutionary change helped the disease to keep its hosts — be they rat or human — alive for longer, thereby enabling it to spread more widely. This adaptation may have been especially necessary after populations of the plague's primary hosts, rats, were killed off en masse during outbreaks. "The reduction of pla may reflect the changing size and density of rodent and human populations," Poinar said. "It's important to remember that plague was an epidemic of [flea-ridden] rats, which were the drivers of epidemics and pandemics. Humans were accidental victims." The scientists say that further research into both ancient and contemporary plague strains could reveal more pla depletions and help them to better understand how such changes to the germ's genome have shaped its virulence through history. Nowadays, Y. pestis infections can be cured with antibiotics, though some strains have shown troubling signs of antibiotic resistance. To head off the threat of a superbug plague outbreak, scientists in the U.K. have already started developing a bubonic plague vaccine to add to stockpiles. This article is for informational purposes only and is not meant to offer medical advice.
GMA Network
3 days ago
- Health
- GMA Network
Plague became less deadly to last longer, study finds
PARIS, France - The bacteria that cause the plague evolved to become less deadly over time, allowing it to continue infecting people in three separate pandemics over more than a thousand years, new research said Thursday. The first pandemic -- the plague of Justinian -- struck in the 500s at the start of the Middle Ages and lasted for around 200 years. The Black Death began in the mid-1300s and would become the deadliest pandemic in human history, killing up to half of the people in Europe, western Asia and Africa, with outbreaks continuing for centuries. The third bubonic plague pandemic broke out in China in the 1850s and continues today, with some cases still being recorded in parts of sub-Saharan Africa. "The plague bacteria have a particular importance in the history of humanity, so it's important to know how these outbreaks spread," said Javier Pizarro-Cerda, a microbiologist at France's Pasteur Institute and co-author of the study published in the journal Science on Thursday. The researchers examined samples of Yersinia pestis, the bacteria that cause the plague, dating back to each pandemic. In all three cases, the genes of each plague bacteria evolved to become less virulent and less deadly over time, according to the study. By causing less severe infections, the bacteria are thought to have extended the length of the pandemics because it gained more opportunities to spread between people. The researchers confirmed this theory by infecting rats with recent plague samples, showing that the disease lasted longer when the virulence decreased. While antibiotics can now effectively fight off the plague, the research could shine a light on how other pandemics might evolve. "This allows us to gain a comprehensive understanding of how pathogens can adapt to different situations," Pizarro-Cerda said. "We finally better understand what the plague is -- and how we can develop measures to defend ourselves," he added. — Agence France-Presse
Yahoo
3 days ago
- General
- Yahoo
How the bubonic plague has survived for centuries
The catastrophic loss of life at the hands of a single bacterium during the 14th century remains one of human history's most devastating events. Yersinia pestis–the bacterium that causes bubonic plague–managed to survive for centuries by adjusting its severity and the length of time it takes to kill its hosts. Despite that virulence, some forms of plague did ultimately die out. Now, scientists have documented the way that one single gene in Yersinia pestis made it so adaptable. The findings are described in a study published May 29 in the journal Science. [ Related: Bubonic plague discovered in ancient Egyptian mummy DNA. ] According to the Cleveland Clinic, there are three types of plague. Which type that you have depends on where in your body Yersinia pestis ends up. Bubonic plague infects the lymph nodes, septicemic plague is in the blood, and pneumonic plague affects the lungs. Yersinia pestis itself is a bacterium with some deep historical roots and has caused three major pandemics in recorded human history. The Plague of Justinian in the mid-500s is the first recorded plague pandemic in human history. It is named for Justinian I, the Byzantine emperor at that time, and it devastated the Mediterranean region. Mortality estimates vary between 25 million and 100 million deaths. It killed roughly 40 percent of Constantinople's (now Istanbul) population, which was the most important center of cultural and political life in the world. at the time. It eventually led to the second plague pandemic–the Black Death in the 14th century. The Black Death is still the deadliest pandemic in recorded human history, killing 30 to 50 percent of the population in Europe, Western Asia, and Africa. The disease re-emerged in several waves over more than 500 years and persisted in that form until 1840. The third plague pandemic began in China in 1855 and continues today. Antibiotics have significantly helped treat the disease, but its impacts are still felt in parts of Madagascar and the Democratic Republic of Congo, where cases are regularly reported. Strains of the original Justinian plague went extinct after 300 years of wreaking havoc on European and Middle Eastern populations. The strains that caused the Black Death emerged from infected rodents before it broke into two major lineages. One of these two lineages is the ancestor of the present-day strains, while the other strain re-emerged over centuries in Europe and went extinct by the early 19th century. 'This is one of the first research studies to directly examine changes in an ancient pathogen, one we still see today, in an attempt to understand what drives the virulence, persistence and/or eventual extinction of pandemics,' Hendrik Poinar, a study co-author and molecular evolutionary geneticist and biological anthropologist at McMaster University in Canada, said in a statement. In the new study, the team used hundreds of samples from ancient and modern plague victims. They screened the samples for a gene known as pla. This gene helps Yersinia pestis move through the body's immune system undetected by the lymph nodes before it spreads to the rest of the body. The genetic analysis revealed that its copy number–the total number of pla genes found in the bacterium–actually decreased in the later plague outbreaks. This decreased mortality by about 20 percent, while increasing the length of infection. The hosts typically lived longer before they died. These studies were performed in mice models of bubonic plague, according to the team. When the pla gene was in its original, high copy number, the disease was much more virulent. It killed all of its hosts and did so much quicker. Additionally, the team also pinpointed a similarity between the trajectories of both modern and ancient strains. These strains independently evolved similar reductions in the pla gene during the later stages of the first and second plague pandemics and in three samples from the third pandemic that were uncovered in present day Vietnam. In both the Justinian plague from the 500s and the Black Death, the evolutionary change occurred approximately 100 years after the first outbreaks. The team believes that when the gene copy number dropped and the infected rats lived longer, the rodents could spread infection farther. This spread helped ensure the pathogen's reproductive success. 'The reduction of pla may reflect the changing size and density of rodent and human populations,' explained Poinar. 'It's important to remember that plague was an epidemic of rats, which were the drivers of epidemics and pandemics. Humans were accidental victims.' Due to their high numbers and proximity to humans, the black rats in cities likely acted as 'amplification hosts.' Since these black rats are highly susceptible to Yersinia pestis themselves, the pathogen needed the rat populations to stay high enough to supply new hosts for Yersinia pestis to persist and allow the natural pandemic cycle to continue. [ Related: DNA from plague victims' teeth may unravel the origin of Black Death. ] However, the strains of plague that did not have the pla gene eventually went extinct. This likely reflects another shift that occurred in the host-pathogen relationship within their environment. When the team searched for signs of pla gene depletion in samples of the third plague pandemic preserved in a large collection at the Institut Pasteur in Paris, they found three contemporary strains with the pla depletion. The diminished virulence that the pathogen evolved in response to more of its hosts dying potentially caused these earlier plague pandemics to fizzle out. 'Thanks to our international collaborators who monitor local epidemics of plague worldwide, we were able to find the unique bacterial samples used for this project, akin to finding of three rare needles in a haystack,' Javier Pizarro-Cerdá, a study co-author and microbiologist who specializes in plague at the Institut Pasteur, said in a statement. Despite this evolution, most of the strains circulating in some countries in Africa, South America, and Asia are more virulent. 'Today, the plague is a rare disease, but one that remains a public health concern and serves as a model for gaining a broad understanding of how pandemics emerge and become extinct,' said Javier Pizarro-Cerdá. 'This example illustrates the balance of virulence a pathogen can adopt in order to spread effectively from one host to another.'
Straits Times
3 days ago
- Health
- Straits Times
Plague bacteria became less deadly to last longer, study finds
Yersinia pestis bacteria infected people in three separate pandemics over more than a thousand years by becoming less deadly. PHOTO: AFP Plague bacteria became less deadly to last longer, study finds PARIS - The bacteria that caused the plague evolved to become less deadly over time, allowing it to continue infecting people in three separate pandemics over more than a thousand years, new research said on May 29. The first pandemic – the plague of Justinian – struck in the 500s at the start of the Middle Ages and lasted for around 200 years. The Black Death began in the mid-1300s and would become the deadliest pandemic in human history, killing up to half of the people in Europe, western Asia and Africa, with outbreaks continuing for centuries. The third bubonic plague pandemic broke out in China in the 1850s and continues today, with some cases still being recorded in parts of sub-Saharan Africa. 'The plague bacteria have a particular importance in the history of humanity, so it's important to know how these outbreaks spread,' said Dr Javier Pizarro-Cerda, a microbiologist at France's Pasteur Institute and co-author of the study published in the journal Science on May 29. The researchers examined samples of Yersinia pestis, the bacteria that caused the plague, dating back to each pandemic. In all three cases, the genes of each plague bacteria evolved to become less virulent and less deadly over time, according to the study. By causing less severe infections, the bacteria are thought to have extended the length of the pandemics because it gained more opportunities to spread between people. The researchers confirmed this theory by infecting rats with recent plague samples, showing that the disease lasted longer when the virulence decreased. Yersinia pestis bacteria are pictured under an electron microscope. PHOTO: AFP While antibiotics can now effectively fight off the plague, the research could shine a light on how other pandemics might evolve. 'This allows us to gain a comprehensive understanding of how pathogens can adapt to different situations,' Dr Pizarro-Cerda said. 'We finally better understand what the plague is – and how we can develop measures to defend ourselves,' he added. AFP Join ST's Telegram channel and get the latest breaking news delivered to you.
