Roughly 30 to 60 percent of people in affected communities died during the Black Death of 1347–1351, which means somewhere between 40 and 70 percent survived, depending heavily on the region and the form of plague they contracted. That range is wide because the pandemic was not a single uniform event. Mortality varied by geography, by the type of infection a person developed, and even by the individual’s prior health. Piecing together who survived and why turns out to be a surprisingly active area of research, with skeletal evidence, manorial records, and ancient DNA all reshaping the picture.
How Many People Died, and Where
Historical and archaeological evidence from England suggests the Black Death killed roughly 30 to 60 percent of affected populations.{” “}1PubMed Central. Selective mortality during famine and plague events in medieval London That figure is often simplified to “killed a third to half of Europe,” but the reality was patchier than any single number suggests. A 2022 study using pollen data and land-use records across the continent found that while some regions experienced devastating mortality, others showed negligible or no impact at all. Cultural, ecological, economic, and climatic factors all mediated how severely the disease hit a given area.2PubMed. Palaeoecological data indicates land-use changes across Europe linked to spatial heterogeneity in mortality during the Black Death pandemic
Outside Europe, mortality could be just as catastrophic. In Alexandria, Egypt, one of the first major population centers struck in 1348, contemporary chroniclers recorded daily death tolls climbing from around 100 to as high as 700 or more at the peak. Using workforce estimates and plague-curve modeling, researchers have placed Alexandria’s total mortality at roughly 48 percent of the city’s pre-plague population.3Annales de démographie historique. Refugees of the Black Death: Quantifying rural migration for plague and other environmental disasters These figures underscore a crucial point: survival rates were not fixed. They shifted dramatically from one city or region to another, shaped by population density, trade routes, climate, and local conditions.
Different Forms of Plague, Different Odds
The bacterium behind the Black Death, Yersinia pestis, causes three clinical forms of plague, and your chances of surviving depended enormously on which one you developed.
- Bubonic plague: The most common form, marked by swollen lymph nodes (buboes), fever, and chills. Without treatment, mortality can reach about 60 percent. With modern antibiotics administered early, that drops to less than 5 percent.4Journal of Biosafety and Biosecurity. Deliberate release: Plague – A review – Section: 3.4.1. Bubonic plague
- Pneumonic plague: An infection of the lungs, sometimes arising from untreated bubonic plague, sometimes caught directly by inhaling respiratory droplets. This form is rapidly fatal if untreated, with historical accounts citing a case-fatality rate approaching 100 percent within one to three days of symptom onset.5PubMed Central. Deaths Associated with Pneumonic Plague, 1946-2017
- Septicemic plague: When the bacteria enter the bloodstream directly, causing a systemic infection. This form was also nearly always fatal without intervention.
During the medieval pandemic, most victims likely developed the bubonic form. That 60 percent fatality rate for untreated bubonic plague is the figure most consistent with the population-level mortality estimates of 30 to 60 percent, because not everyone in a community was necessarily exposed, and some people who were exposed may have fought off the infection or developed only a mild case. The truly terrifying pneumonic form spread in crowded conditions and likely pushed mortality higher in densely packed urban centers.
The Plague Did Not Kill at Random
One of the more striking findings from modern research is that the Black Death was selective. It did not mow down every age and condition equally. An analysis comparing skeletons from London’s East Smithfield cemetery, which was specifically opened to bury Black Death victims, with normal medieval cemeteries in Denmark found that the plague was selective with respect to frailty. People who were already in poorer health before the epidemic were more likely to die.6PubMed Central. Selectivity of black death mortality with respect to preexisting health In practical terms, the Black Death targeted elderly adults and people who had been previously exposed to physiological stressors, such as famine, chronic infection, or nutritional deficiency.7PubMed. Health in post-Black Death London (1350-1538): age patterns of periosteal new bone formation in a post-epidemic population
That selectivity was not as strong as what you’d see in a normal year. In non-epidemic times, frail individuals die at much higher rates than healthy ones, simply because everyday stressors are enough to push them over the edge. The Black Death was less discriminating than normal mortality, meaning it killed plenty of otherwise healthy people too, but it still leaned toward those who were already weakened. Younger, healthier individuals had better odds, even if those odds were far from guaranteed.
Did Sex or Social Status Matter?
Whether men or women survived the Black Death at different rates has been the subject of several bioarchaeological studies, and the answer is not as straightforward as you might expect. An analysis of London’s Black Death victims found that sex did not strongly affect risk of death during the epidemic.8PubMed. The effect of sex on risk of mortality during the Black Death in London, A.D. 1349-1350 Women in medieval England faced considerable social inequality, including worse access to food and resources in some contexts, but that disadvantage did not translate into a higher susceptibility to plague infection itself.9PubMed. Survival analysis of the Black Death: Social inequality of women and the perils of life and death in Medieval London
More recent work has complicated this picture somewhat. A 2025 study examining the intersection of age, sex, and social risk found that middle-aged males had higher mortality risk during the Black Death, possibly due to differences in social buffering and biological resilience.10PubMed. Who the Plague Chose: Exploring Intersecting Social Risk in Black Death Mortality The researchers interpreted this as evidence that the pandemic amplified pre-existing biological and social vulnerabilities in complex ways. In short, biological susceptibility seems to have mattered more than social disadvantage alone, but the two interacted. Poverty, malnutrition, and poor living conditions likely contributed to the “frailty” that made some people more vulnerable, even if social class per se wasn’t as decisive as you might assume.
What Recovery Actually Looked Like
Medieval chroniclers often claimed that plague victims either died within three or four days or recovered. That timeline turns out to be misleadingly fast. An exceptional set of manorial records from Warboys, Huntingdonshire, documents twenty-two customary tenants who fell ill during the summer of 1349 and were excused from their labor services. At least fourteen of those twenty-two can be positively identified in later records, confirming that they survived, and the actual number of survivors was likely higher since many subsequent records simply didn’t survive the centuries.11Oxford Academic. Surviving the Black Death in medieval England: recovering from illness at Warboys, Huntingdonshire
What makes the Warboys records remarkable is the timeline. Rather than the three-to-four-day narrative of the chroniclers, these tenants took three to four weeks before reintegrating into society. Some may have lingered at home because they were still weak, and others may have been reluctant to venture back out for fear of spreading or re-catching the disease. The evidence suggests medieval people had some practical understanding of isolation, even if germ theory lay centuries in the future. These records offer a rare window into what survival looked like on the ground: a slow, uncertain convalescence rather than a quick bounce-back.
How the Plague Spread and Why That Shaped Survival
For decades, the standard story held that plague spread primarily through rat fleas. Rats carried the bacterium, fleas bit the rats, then bit humans. The role of rats was real, but research has increasingly highlighted the importance of human ectoparasites, specifically body lice and human fleas, in spreading plague during the Second Pandemic. A modeling study using Bayesian inference found that a human-ectoparasite transmission model fit historical mortality curves from nine European outbreaks better than models for pneumonic or rat-based transmission.12PubMed Central. Human ectoparasites and the spread of plague in Europe during the Second Pandemic
This matters for survival because the mode of transmission influenced who got exposed. Body lice and human fleas thrive in the close, unwashed quarters of medieval life, which means crowded households and poor sanitation likely drove transmission more than proximity to rats alone. Temperature also played a role. Flea transmission efficiency is sensitive to climate: experiments with Xenopsylla cheopis, the rat flea, found that transmission was most efficient at around 23°C, with declining efficiency at both higher and lower temperatures.13PubMed Central. Effects of temperature on the transmission of Yersinia Pestis by the flea, Xenopsylla Cheopis, in the late phase period Regions with climates outside that sweet spot may have seen slower or less intense transmission, contributing to the geographic variation in mortality.
The Plague Came Back, But Killed Fewer People
The Black Death of 1347–1351 was only the first wave. A second major outbreak, known as the pestis secunda, struck England in 1361 and killed an estimated 10 to 30 percent of affected populations, significantly lower than the first wave but still catastrophic by any normal standard.1PubMed Central. Selective mortality during famine and plague events in medieval London Plague continued to recur across Europe for centuries, with major outbreaks in the 1370s, the 1600s, and as late as the Great Plague of London in 1665.
Why did later waves tend to kill fewer people? Several factors likely contributed. The first wave had already removed the most vulnerable individuals from the population, a brutal form of selection. Survivors may have had some degree of acquired immunity or were simply hardier to begin with. Behavioral changes likely played a role as well: quarantine measures became more formalized over successive outbreaks, and some communities developed rudimentary public health responses. And one intriguing modeling study has suggested that the spread of the brown rat (Rattus norvegicus), which tends to live in wetter habitats and may have acquired partial herd immunity through exposure to environmental Yersinia species, helped divert fleas away from human hosts and contributed to the eventual disappearance of plague epidemics from Europe in the 18th century.14PubMed. Modelling the black death. A historical case study and implications for the epidemiology of bubonic plague
Did the Black Death Change Human Genetics?
The scale of mortality during the Black Death was so vast that researchers have asked whether it left a permanent mark on the human genome. A 2022 study in Nature analyzed ancient DNA from individuals who lived before, during, and after the pandemic in London and Denmark. The researchers identified 245 genetic variants that appeared to shift in frequency, and four of those were replicated in an independent Danish cohort. One variant in particular, associated with the gene ERAP2, appeared to help macrophages control intracellular Y. pestis more effectively. People carrying the protective version of this variant may have been more likely to survive the plague, passing the allele on at higher rates.15PubMed Central. Evolution of immune genes is associated with the Black Death A separate study examining HLA genes, which are central to both innate and adaptive immunity, also found evidence consistent with natural selection driven by plague exposure.16Molecular Biology and Evolution. Analysis of Genomic DNA from Medieval Plague Victims Suggests Long-Term Effect of Yersinia pestis on Human Immunity Genes
This is where the evidence gets contentious. A 2024 response, also published in Nature, argued that the original ERAP2 findings were insufficiently supported, raising concerns about sample sizes, statistical methods, and whether the observed allele frequency shifts could be explained by genetic drift rather than selection.17PubMed Central. Insufficient evidence for natural selection associated with the Black Death The debate is ongoing. What’s not disputed is that the idea is plausible in principle: a pandemic killing 30 to 60 percent of a population is exactly the kind of event that could drive rapid evolutionary change. Whether specific genes have been convincingly identified as beneficiaries of that selection is another question, and the field is still working it out.
One provocative finding from the original 2022 study is worth noting: the alleles that appear to have been protective against plague overlap with variants that today are associated with increased susceptibility to autoimmune diseases like Crohn’s disease and rheumatoid arthritis. If the link holds up, it would mean that the genetic legacy of surviving the plague comes with a cost centuries later, a kind of evolutionary trade-off where yesterday’s survival advantage becomes today’s chronic disease risk.
Surviving Plague Today
Plague still exists. Several thousand cases are reported globally each year, mostly in parts of Africa, Central Asia, and the Americas. The United States sees a handful of cases annually, typically in the rural Southwest. The critical difference between modern plague and its medieval ancestor is antibiotics. Several classes of drugs, including tetracyclines, fluoroquinolones, and aminoglycosides, are effective against the vast majority of Y. pestis strains.18PubMed Central. Antibiotic Therapy of Plague: A Review Early treatment is the key variable: diagnosed quickly, even bubonic plague has a fatality rate under 5 percent.4Journal of Biosafety and Biosecurity. Deliberate release: Plague – A review – Section: 3.4.1. Bubonic plague Delayed treatment, especially for pneumonic plague, remains dangerous.
No widely used vaccine exists for plague today, and only monotherapy (a single antibiotic) is currently recommended; combination therapy has not shown benefits in preclinical studies or case reports.18PubMed Central. Antibiotic Therapy of Plague: A Review The real threat in a modern context is not that plague can’t be treated, but that it can be missed. Doctors in regions where plague is rare may not consider the diagnosis quickly enough, and in pneumonic cases, even a day’s delay can be fatal. Medieval Europe had no such tools. The survival rates of the 1340s reflect what happens when Yersinia pestis meets an immunologically naive, malnourished, densely packed population with no antibiotics and only a hazy understanding of how disease spreads. That roughly 40 to 70 percent of people survived at all speaks to both the variability of the disease and the resilience of the human immune system under extraordinary pressure.