When the plague returned in —and again in , , , and —DeWitte looked for signs that the population might have been healthier and better fed: Were they taller with fewer signs of lesions? She looked at skeletons from cemeteries used before the Black Death and skeletons from another that was in use from just after the plague hit until , gathering comparable data to her previous work.
Looking simply at age at death, DeWitte found that a higher proportion of people lived to older ages after the Black Death. That is, if you or your parents or grandparents lived through the first plague epidemic, you were more likely to survive until you reached age 50 or above.
Descendants of plague survivors were more likely to live through their reproductive years, thus passing on whatever genetic advantages enabled their ancestors to survive the plague. These documents showed spikes in mortality associated with plague epidemics in , , , , and However, wills and other documents tend to provide evidence only on well-to-do men, excluding married or unmarried women, children, servants, apprentices, laborers, and paupers.
The medieval population of England dropped precipitously when the plague reached London in The effects on the population were felt for centuries afterward. Figure adapted by Barbara Aulicino from S. Broadberry, B.
Campbell, and B. DeWitte argues that her bioarchaeological data provide information about a much broader sweep of medieval society. Despite repeated plague outbreaks and other episodes of crisis mortality, such as famines or volcanic eruptions, her study indicates that the general population enjoyed a period of at least years during which mortality and survival overall improved compared to conditions before and during the Black Death.
Did such a strong selective event produce changes that can be seen today? Two genetically distinct but adjacent populations offered a rare opportunity to document the plague's evolutionary effects. A recent study has pointed to another possibility. A team led by Jaume Bertranpetit and Mihai G. Netea decided to investigate genetic differences between Romanian Europeans and people who lived in the same area of Romania but were of Rroma ancestry traditionally identified as Gypsies.
Linguistic and genetic documentation indicates that the Rroma migrated from northwest India between the 5th and 11th centuries, when they began to settle in Romania. Over the centuries, the Rroma remained largely isolated from Romanians of European descent, although they lived in the same region. Thus the infectious agents that potentially shaped the Rroma genomes during the last millennium—including the plague—were shared with the European Romanians, but their initial genetic backgrounds were different.
Because India did not suffer from the Black Death, the immune-related genes put under positive selection by exposure to the disease should be similar among European Romanians and Rroma but different from those among Indians in Gujarati, home of the populations ancestral to the Rroma.
The team assayed almost , small genetic changes known as single nucleotide polymorphisms SNPs , which are often used as a proxy for genomic differences among cohorts of people. Then they analyzed the results looking for genes under positive selective pressure among the Rroma and European Romanians but not shared by the northwest Indians. Four genes on chromosome 4 met these criteria.
Three of the four genes in this cluster are so-called TLR genes involved in recognizing pathogens such as bacteria and initiating an immune, anti-inflammatory response. If you have been exposed to rodents or fleas, or if you have visited a region where plague is known to occur, and you develop symptoms of plague, contact your doctor immediately:. When you visit the doctor, emergency room, or anywhere else where others are present, wear a surgical mask to prevent the spread of the disease.
If your doctor suspects you may have plague, they will check for the presence of the bacteria in your body:. The samples will be sent to a laboratory for analysis. Preliminary results may be ready in just two hours, but confirmatory testing takes 24 to 48 hours.
Often, if the plague is suspected, your doctor will begin treatment with antibiotics before the diagnosis is confirmed. This is because the plague progresses rapidly, and being treated early can make a big difference in your recovery. The plague is a life-threatening condition that requires urgent care.
With no treatment, bubonic plague can multiply in the bloodstream causing septicemic plague or in the lungs causing pneumonic plague. Death can occur within 24 hours after the appearance of the first symptom. Treatment usually involves strong and effective antibiotics such as gentamicin or ciprofloxacin, intravenous fluids, oxygen, and, sometimes, breathing support. Medical personnel and caregivers must take strict precautions to avoid getting or spreading plague.
Plague can lead to gangrene if blood vessels in your fingers and toes disrupt blood flow and cause death to tissue. In rare cases, plague can cause meningitis, an inflammation of membranes that surround your spinal cord and brain. Keeping the rodent population under control in your home, workplace, and recreation areas can greatly reduce your risk of getting the bacteria that causes plague. Keep your home free from stacks of cluttered firewood or piles of rock, brush, or other debris that could attract rodents.
Protect your pets from fleas using flea control products. Pets that roam freely outdoors may be more likely to come into contact with plague-infected fleas or animals.
If you live in an area where the plague is known to occur, the CDC recommends not allowing pets that roam freely outside to sleep in your bed. If your pet becomes sick, seek care from a veterinarian right away. Use insect repellent products or natural insect repellants like oil of lemon eucalyptus when spending time outdoors. If you have been exposed to fleas during a plague outbreak, visit your doctor immediately so your concerns can be addressed quickly.
Epidemics of plague killed millions of people about one-quarter of the population in Europe during the Middle Ages. Plague Transmission Learn more. Ecology and Transmission. Diagnosis and Treatment. Information for Healthcare Professionals. Maps and Statistics. Once these cells are knocked out, the bacteria can multiply unhindered. Many small mammals act as hosts to the bacteria, including rats, mice, chipmunks, prairie dogs, rabbits, and squirrels.
During an enzootic cycle , Y. When the bacteria pass to other species, during an epizootic cycle, humans face a greater risk for becoming infected with plague bacteria. Rats have long been thought to be the main vector of plague outbreaks, because of their intimate connection with humans in urban areas. Scientists have more recently discovered that a flea that lives on rats, Xenopsylla cheopis , primarily causes human cases of plague.
When rodents die from the plague, fleas jump to a new host, biting them and transmitting Y. Transmission also occurs by handling tissue or blood from a plague-infected animal, or inhalation of infected droplets.
Bubonic plague , the disease's most common form, refers to telltale buboes—painfully swollen lymph nodes—that appear around the groin, armpit, or neck. Pneumonic plague , the most infectious type, is an advanced stage of plague that moves into the lungs.
If untreated, bubonic and pneumonic plague can progress to septicemic plague , infecting the bloodstream. If left untreated, pneumonic and septicemic plague kills almost percent of those it infects. Three particularly well-known pandemics occurred before the cause of plague was discovered.
The first well-documented crisis was the Plague of Justinian, which began in A. Named after the Byzantine emperor Justinian I, the pandemic killed up to 10, people a day in Constantinople modern-day Istanbul, Turkey , according to ancient historians.
Modern estimates indicate half of Europe's population—almost million deaths—was wiped out before the plague subsided in the s. Arguably the most infamous plague outbreak was the so-called Black Death , a multi-century pandemic that swept through Asia and Europe.
It was believed to start in China in , spreading along trade routes and reaching Europe via Sicilian ports in the late s. The Black Death lingered on for centuries, particularly in cities. Outbreaks included the Great Plague of London , in which 70, residents died. The cause of plague wasn't discovered until the most recent global outbreak, which started in China in and didn't officially end until The pandemic caused roughly 10 million deaths.
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