The Black Death was the largest and deadliest pandemic of Yersinia pestis recorded in human history, and likely the most infamous individual pandemic ever documented. The plague originated in the Eurasian Steppes, before moving with Mongol hordes to the Black Sea, where it was then brought by Italian merchants to the Mediterranean. From here, the Black Death then spread to almost all corners of Europe, the Middle East, and North Africa. While it was never endemic to these regions, it was constantly re-introduced via trade routes from Asia (such as the Silk Road), and plague was present in Western Europe until the seventeenth century, and the other regions until the nineteenth century. Impact on Europe In Europe, the major port cities and metropolitan areas were hit the hardest. The plague spread through south-western Europe, following the arrival of Italian galleys in Sicily, Genoa, Venice, and Marseilles, at the beginning of 1347. It is claimed that Venice, Florence, and Siena lost up to two thirds of their total population during epidemic's peak, while London, which was hit in 1348, is said to have lost at least half of its population. The plague then made its way around the west of Europe, and arrived in Germany and Scandinavia in 1348, before travelling along the Baltic coast to Russia by 1351 (although data relating to the death tolls east of Germany is scarce). Some areas of Europe remained untouched by the plague for decades; for example, plague did not arrive in Iceland until 1402, however it swept across the island with devastating effect, causing the population to drop from 120,000 to 40,000 within two years. Reliability While the Black Death affected three continents, there is little recorded evidence of its impact outside of Southern or Western Europe. In Europe, however, many sources conflict and contrast with one another, often giving death tolls exceeding the estimated population at the time (such as London, where the death toll is said to be three times larger than the total population). Therefore, the precise death tolls remain uncertain, and any figures given should be treated tentatively.

Bubonic plague was a constant threat to Afro-Eurasian populations during the Second Plague pandemic. This pandemic arrived in Europe as the Black death in 1347, and although it never became endemic, it was constantly re-introduced to the continent over the next four centuries. By the late seventeenth century, most regions of Europe had recorded their final epidemics (but not necessarily the final cases), and it eventually subsided in the mid-nineteenth century. The death tolls due to plague were relatively low in most years, however, when epidemics appeared they could often decimate populations within a few short years, and lead to mass evacuations of major cities (such as in London in 1665). Plague in Russia Of the sample epidemics shown here, the two largest cases were in Russia; a region where plague outbreaks were much more frequent than in other parts of Europe. The reason for this was because plague would spread along the Volga river, after being brought to the Caspian Sea by fishermen from the Eurasian Steppes (where the plague bacteria Yersinia pestis is thought to originate). Between these two epidemics, it is estimated that Russia lost over half a million people. The epidemic of 1709, which spread across Northern Europe during the Great Northern War, saw a reported 150,000 deaths across the Russian Empire. The plague epidemic of 1771 in Russia saw the deaths of approximately 60,000 in the capital city, and as many as 300,000 in the surrounding region. In Moscow, the government's attempts to contain the outbreak resulted in a riot by the citizens, and the aftermath saw significant socio-political upheaval in the city and beyond.

The Plague of Justinian was an outbreak of bubonic plague that ravaged the Mediterranean and its surrounding area, between 541 and 767CE. It was likely the first major outbreak of bubonic plague in Europe, and possibly the earliest pandemic to have been recorded reliably and with relative accuracy. Contemporary scholars described the symptoms and effects of the disease in detail, and these matched descriptions of the Black Death and Third Pandemic, leading most historians to believe that this was bubonic plague. It was also assumed that the plague originated in sub-Saharan Africa, before making its way along the Nile to Egypt, and then across the Mediterranean to Constantinople. In 2013, scientists were able to confirm that Justinian's Plague was in fact Yersinia pestis (the bacteria which causes bubonic plague), and recent theories suggest that the plague originated in the Eurasian Steppes, where the Black Death and Third Pandemic are also thought to have originated from, and that it was brought to Europe by the Hunnic Tribes of the sixth century. Plague of Justinian The pandemic itself takes its name from Emperor Justinian I, who ruled the Byzantine Empire (or Eastern Roman Empire) at the time of the outbreak, and who actually contracted the disease (although he survived). Reports suggest that Constantinople was the hardest hit city during the pandemic, and saw upwards of five thousand deaths per day during the most severe months. There are a multitude of sources with differing estimates for the plague's death toll, with most ranging between 25 and 100 million. Until recently, scholars assumed that the plague killed between one third and 40 percent of the world's population, with populations in infected regions declining by up to 25 percent in early years, and up to 60 percent over two centuries. The plague was felt strongest during the initial outbreak in Constantinople, however it remained in Europe for over two centuries, with the last reported cases in 767. Pre-2019 sources vary in their estimates, with some suggesting that up to half of the world's population died in the pandemic, while others state that it was just a quarter of the Mediterranean or European population; however most of them agree that the death toll was in the tens of millions. Historians have also argued about the plague's role in the fall of the Roman Empire, with opinions ranging from "fundamental" to "coincidental", although new evidence is more aligned with the latter theories. Challenging theories As with the recent studies which propose a different origin for the disease, one study conducted by researchers in Princeton and Jerusalem calls into question the accuracy of the death tolls estimated by historians in the 19th and 20th centuries. In 2019, L. Mordechai and M. Eisenberg published a series of papers suggesting that, although the plague devastated Constantinople, it did not have the same impact as the Black Death. The researchers argue that modern historians have taken a maximalist approach to the death tolls of the pandemic, and have applied the same models of distribution to Justinian's Plague as they believe occurred during the Black Death; however there is little evidence to support this. They examine the content and number of contemporary texts, as well archaeological, agricultural and genetic evidence which shows that the plague did spread across Europe, but did not seem to cause the same societal upheaval as the Black Death. It is likely that there will be further investigation into this outbreak in the following years, which may shed more light on the scale of this pandemic.

The Black Death, possibly the deadliest and most well-known pandemic in human history, arrived in Europe from the Eurasian Steppes in 1347 and killed as much as 60 percent of the population within the next five years. While this outbreak eventually subsided, it was just the beginning of the Second Plague Pandemic; the bubonic plague was never really endemic to Europe, but was continuously re-introduced to Europe and the Mediterranean region via trade from Asia. Plague in the interim Following the Black Death, outbreaks of plague were sporadic, and varied in severity; however the lack of understanding and treatment meant that these outbreaks had incredibly high fatality rates and often decimated large portions of infected populations. For example, London lost up to one quarter of its population to plague epidemics in the 1560s, and again in the 1660s, while more than a century later Moscow and the surrounding region reportedly lost several hundred thousand people to plague within two years. Smaller and more isolated communities, such as in Cyprus, Iceland, and Malta were hit infrequently but severely; Iceland reportedly lost two thirds of its total population in a single pandemic in the early 1400s. Decline in Europe Over four centuries after its arrival in Europe, epidemics began to wean on larger scales. Ireland recorded its final epidemic in 1650, and the trend then continued across the states of mainland Europe in the next few decades. After plague disappeared from the German states in the 1680s, there were no more plague epidemics recorded in North or Western Europe. Despite this, it would be almost 160 years before plague disappeared from the Balkans and Turkey. As of 1841, the only part of Europe where plague was still endemic was along the Volga river in Russia; it was brought there by fisherman to the Caspian Sea from Persia and the Eurasian Steppe region.

As early as 1319, allegations of well-poisoning had been levelled at leper communities in Europe, in an attempt to demonize and ostracize this group in society. In France and Spain in 1321, the "leper's plot" developed into a widespread conspiracy, claiming that leper communities were acting on the orders of the Jews or Spanish Moors, poisoning water supplies in an attempt to spread disease among Christians. Under royal decrees, many lepers were then tortured into confessing to these acts, and were subsequently burnt at the stake (although this was often carried out by vigilante mobs before it could be done by the courts). After the initial hysteria in 1321, the involvement of lepers was quickly dismissed, and a papal bull was introduced to grant protection to leper communities in France; this however did not dispel the myths surrounding the Jews' involvement in the conspiracy, and the issue emerged again a few decades later. Why the Jews were blamed When the bubonic plague made its way to Europe, many were eager to find a scapegoat on whom they could blame their misfortune. The "well-poisoning" accusations were quickly raised again against Jewish communities in France and Spain, and also across the German states. Historians point to several reasons why Jews were blamed for the Black Death; many Jews lived in separate communities and did not use the same common wells, and Jewish religious practices promote bathing and hand-washing; both of these factors meant that the plague spread differently and at a different rate among Jews than it did among the general population. Modern historians also point to the fact that Jews were often moneylenders, and their debtors often used the plague as an opportunity to expunge their debts; Holy Roman Emperor Charles IV also forfeited the property of Jews who were killed in the pogroms, giving further impetus to these mobs. Anti-Jewish pogroms The first reported pogroms took place in Toulon in 1348, before the violence then spread across the rest of Western Europe. Over the next three years, hundreds of Jewish communities were attacked and exterminated, with the majority taking place in the German states. A number of larger communities, such as those in Cologne and Mainz, were destroyed completely, resulting in the deaths and forced conversions of thousands of Jews. Pope Clement VI introduced two papal bulls in 1348, which granted the church's protection to Europe's Jews. He also urged the clergy and nobility to take measures that protected Jews in their local areas, although most sources show that authorities were apathetic or complicit in the actions of the mobs. There is even evidence that authorities orchestrated several of the pogroms, such as in Strasbourg, where authorities led the city's Jewish community to a newly-built house outside the city, but when they arrived, any Jews who refused to convert to Christianity were then burned alive inside the house. Legacy Many of the sources present different versions of events, with death tolls ranging from one hundred to several thousand in some cases, while some sources also claim that Jews set fire to their own homes rather than convert. It is now impossible to confirm the exact sequence of events, or the actual number of deaths resulting from these pogroms, however, the limited sources available do provide a brief foundation for the modern understanding of medieval anti-Semitism and the destruction inflicted upon the Jews during the plague. It is also important to note that these pogroms were not unique to the Black Death's outbreak, and there is evidence of numerous massacres of Jewish communities in the centuries that followed. The demographic impact of the massacres was that there was a mass exodus of Jews from west to Eastern Europe, to countries such as Poland (where they were actually welcomed by authorities). The consequences of this demographic shift would be most felt six centuries later, when millions of Jews across Eastern Europe were exterminated at the hands of the Nazi regime during the Holocaust.

The Plague of Justinian was the first major bubonic plague pandemic recorded in Europe, and was the first pandemic to ever be described or documented with any relative reliability. The plague takes its name from Emperor Justinian I, who ruled the Byzantine Empire (Eastern Roman Empire) at the time of the outbreak. The Byzantine capital of Constantinople (also known then as Byzantium, and Istanbul today) was the hardest hit city during the pandemic, and where the majority of sources are from. Until recently, it was only assumed that the outbreak was bubonic plague, due to the symptoms described by contemporary historians, but scientists were able to confirm that it was in fact Yersinia pestis (the bacterium that causes plague) in 2013. Constantinople overwhelmed It is thought that the plague was brought to Constantinople by Egyptian grain merchants, although a recent theory suggests it was brought from the Eurasian Steppes (from where Yersinia pestis originates) to Europe by Hunnic tribes. While the exact origins of the plague remain unclear, it is estimated that up to 300,000 people died in Constantinople in the first year of the outbreak. Contemporary sources claim that there were approximately 5,000 deaths in the city every day at the height of the pandemic, even reaching highs of 10,000 on some days. Constantinople outbreak was unique A 2019 study, conducted by researchers from Jerusalem and Princeton raises some important questions about the scale of the outbreak across Europe. They dispute the claim by some modern historians that this pandemic killed up to half of the population of the Mediterranean (or that it was instrumental to the collapse of the Eastern Roman Empire), instead suggesting that the scale of the outbreak in Constantinople was unique to that city. They use a variety of literary, archeological, and scientific sources to show that the plague was unlikely to have reached this magnitude across other cities at the time, nor did it spread in the same way that the Black Death did six centuries later. While future studies are likely to provide further insight into these theories, it is important to remember this contrasting hypothesis when studying pre-2019 sources.

Although the Black Death peaked in Europe between 1348 and 1351, plague was almost always present in Britain for the next four centuries. In most years, plague was a dormant threat that affected very few people, and diseases such as smallpox and influenza were much more widespread; however, bubonic plague was prone to outbreaks that could decimate populations in a few short years. In London, plague outbreaks occurred every few decades, usually with death tolls in the tens of thousands. The duration and severity of these epidemics varied, sometimes having high death tolls but subsiding quickly, while others had relatively lower death tolls but could last for a number of years. As London's population and density also grew drastically during this period, plague affected the city differently in the sixteenth and seventeenth centuries. Great Plague of London The final major plague epidemic observed in Britain took place in 1665 and 1666. It became known as the "Great Plague" as it was the last of its kind in Britain, and its death toll eclipsed all other epidemics in the preceding century (although it was much smaller than that of the Black Death). The plague lasted for eighteen months, and had a reported death toll of more than 70,000 in this time; although modern historians estimate that the actual death toll exceeded 100,000. At its peak in September 1665, it is reported that there were more than 7,000 deaths per week, although this may have also been much higher due to the limited records kept at the time. Another reason for the lack of accurate records relating to this epidemic is because of the Great Fire of London in 1666. The fire started on September 02. 1666, and destroyed almost all of the city within the walls, leaving thousands homeless. Historians continue to debate the fire's significance, some citing that it destroyed the unsanitary dwellings where infected rats lived and drove them from the city, while others claim that the timings were purely coincidental and that the epidemic had already begun to subside in February.

The plague outbreak in Bombay around the turn of the twentieth century was the most fatal plague epidemic documented in any city in the past 130 years. Between September 1896 and May 1897, the Municipal Hospital of Bombay reported a fatality rate in plague cases of 61.5 percent. The fatality rate among plague cases ranged between 38 and 82 percent in different months, was highest in the winter. The reason for the peak in February in Bombay is because the temperatures and climate in these months provide the optimal conditions for the breeding of rats and fleas; in contrast to this, earlier epidemics in Europe typically peaked in Autumn, whereas the epidemics in Hong Kong between 1894 and 1902 were hardest felt in May or June.

The Great Northern War was a major conflict in Europe at the beginning of the eighteenth century, and saw Russia defeat Sweden to become the strongest power in the Baltic region, and emerge as one of the continent's most powerful empires. One of the often-overlooked components of the war was a plague outbreak that killed tens of thousands of people during the war, and also impacted each army's ability to reinforce their numbers or to hold positions in infected towns and villages. Some cities are estimated to have lost more than half of their population during this epidemic, particularly along the coast between modern-day Poland and Estonia; the outbreaks experienced along the Baltic coast during the Great Northern War were sometimes larger and deadlier than the outbreaks experienced during the Black Death. While it is impossible for modern historians to differentiate the extent to which the deaths were due to plague, famine or other diseases during the war, it is generally agreed that bubonic plague was the chief culprit among these causes. This outbreak is just one example of many, which highlights how war has facilitated the outbreak of various epidemics throughout history, other examples include the Great Smallpox Pandemic of the 1870s, or the Spanish Flu outbreak of 1918.

Following the arrival of Spanish colonizers in 1519, namely Hernando Cortes and his 600 conquistadors, the indigenous population of the Mexican valley saw a dramatic decline. In the first two years of conquest, thousands of indigenous Americans perished while fighting the European invaders, including an estimated 100,000 who died of violence or starvation during Cortes' siege of the Aztec capital city, Tenochtitlan (present-day Mexico City), in 1520. However, the impact of European violence on population decline pales in comparison to the impact of Old World diseases, which saw the indigenous population of the region drop from roughly 22 million to less than two million within eight decades.. Virgin soil pandemics Almost immediately after the Spanish arrival, a wave of smallpox swept across the indigenous populations, with some estimates suggesting that five to eight million natives died in the subsequent pandemic between 1519 and 1520. This outbreak was not an isolated incident, with the entire indigenous population of the Americas dropping by roughly ninety percent in the next two centuries. The Mexican valley specifically, which was the most populous region of the pre-Columbian Americas, suffered greatly due to virgin soil pandemics (where new diseases are introduced to biologically defenseless populations). In the Middle Ages, the majority of Europeans contracted smallpox as children, which generally granted lifelong immunity. In contrast, indigenous Americans had never been exposed to these diseases, and their populations (of all ages) declined rapidly. Cocoliztli Roughly three decades after the smallpox pandemic, another pandemic swept across the valley, to a more devastating effect. This was an outbreak of cocoliztli, which almost wiped out the entire population, and was followed by a second pandemic three decades later. Until recently, historians were still unsure of the exact causes of cocoliztli, with most hypothesizing that it was a rodent-borne disease similar to plague or an extreme form of a haemorrhagic fever. In 2018, however, scientists in Jena, Germany, studied 29 sets of teeth from 16th century skeletons found in the Oaxaca region of Mexico (from a cemetery with known links to the 1545 pandemic); these tests concluded that cocoliztli was most likely an extreme and rare form of the salmonella bacterium, which caused paratyphoid fever. These pandemics coincided with some of the most extreme droughts ever recorded in North America, which exacerbates the spread and symptoms of this disease, and the symptoms described in historical texts give further credence to the claim that cocoliztli was caused by salmonella.

The Italian city of Venice was one of the largest cities in medieval and Renaissance era Europe. It was the center of the Republic of Venice, a maritime empire in the Mediterranean, and had one of Europe's largest ports for exotic goods (particularly from Asia), or luxury goods such as glassware. Impact of plague While its population was relatively small by modern standards, it is believed that Venice was among the five most populous cities in Western Europe in the given years between 1050 and 1650. The city's population did fluctuate over time due to devastating pandemics, and it is believed that Venice was one of the main points of entry for the Black Death in Europe. Venice was one of the hardest-hit cities during the Black Death; estimates fluctuate greatly across sources, but it is believed that the city lost around 40 percent of its population during the initial outbreak in the 1340s. Decline Furthermore, Venice lost roughly a third of its population during further plague pandemics (both introduced via war) in the 1570s and 1630s. Because of this, the population was kept fairly consistent across the given years between 1600 and 1800. The 18th century also saw the decline of the Venetian Empire, as other states gained power and influence in the Mediterranean. Venice also lost its importance as the entry point of exotic goods into Europe, as other European powers had already established their own maritime empires and trade routes across the globe. Eventually, the crumbling Venetian Empire fell to Napoleon in 1796, and its overseas territories were gradually taken by or split among various other powers. While the empire fell, the city itself continued to be a center for art and culture in Europe, and it has maintained this status until today. In 2021, Venice had a population of more than 250,000 people.

It is estimated that the largest cities in Western Europe in 1330 were Paris and Granada. At this time, Paris was the seat of power in northern France, while Granada had become the largest multicultural city in southern Spain, controlled by the Muslim, Nasrid Kingdom during Spain's Reconquista period. The next three largest cities were Venice, Genoa and Milan, all in northern Italy, renowned as important trading cities during the middle ages. In October 1347, the first wave of the Black Death had arrived in Sicily and then began spreading throughout Europe, decimating the population.

It is only in the past two centuries where demographics and the development of human populations has emerged as a subject in its own right, as industrialization and improvements in medicine gave way to exponential growth of the world's population. There are very few known demographic studies conducted before the 1800s, which means that modern scholars have had to use a variety of documents from centuries gone by, along with archeological and anthropological studies, to try and gain a better understanding of the world's demographic development. Genealogical records One such method is the study of genealogical records from the past; luckily, there are many genealogies relating to European families that date back as far as medieval times. Unfortunately, however, all of these studies relate to families in the upper and elite classes; this is not entirely representative of the overall population as these families had a much higher standard of living and were less susceptible to famine or malnutrition than the average person (although elites were more likely to die during times of war). Nonetheless, there is much to be learned from this data. Impact of the Black Death In the centuries between 1200 and 1745, English male aristocrats who made it to their 21st birthday were generally expected to live to an age between 62 and 72 years old. The only century where life expectancy among this group was much lower was in the 1300s, where the Black Death caused life expectancy among adult English noblemen to drop to just 45 years. Experts assume that the pre-plague population of England was somewhere between four and seven million people in the thirteenth century, and just two million in the fourteenth century, meaning that Britain lost at least half of its population due to the plague. Although the plague only peaked in England for approximately eighteen months, between 1348 and 1350, it devastated the entire population, and further outbreaks in the following decades caused life expectancy in the decade to drop further. The bubonic plague did return to England sporadically until the mid-seventeenth century, although life expectancy among English male aristocrats rose again in the centuries following the worst outbreak, and even peaked at more than 71 years in the first half of the sixteenth century.

Maternal mortality rates can vary significantly around the world. For example, in 2022, Estonia had a maternal mortality rate of zero per 100,000 live births, while Mexico reported a rate of 38 deaths per 100,000 live births. However, the regions with the highest number of maternal deaths are Sub-Saharan Africa and Southern Asia, with differences between countries and regions often reflecting inequalities in health care services and access. Most causes of maternal mortality are preventable and treatable with the most common causes including severe bleeding, infections, complications during delivery, high blood pressure during pregnancy, and unsafe abortion. Maternal mortality in the United States In 2022, there were a total of 817 maternal deaths in the United States. Women aged 25 to 39 years accounted for 578 of these deaths, however, rates of maternal mortality are much higher among women aged 40 years and older. In 2022, the rate of maternal mortality among women aged 40 years and older in the U.S. was 87 per 100,000 live births, compared to a rate of 21 among women aged 25 to 39 years. The rate of maternal mortality in the U.S. has risen in recent years among all age groups. Differences in maternal mortality in the U.S. by race/ethnicity Sadly, there are great disparities in maternal mortality in the United States among different races and ethnicities. In 2022, the rate of maternal mortality among non-Hispanic white women was about 19 per 100,000 live births, while non-Hispanic Black women died from maternal causes at a rate of almost 50 per 100,000 live births. Rates of maternal mortality have risen for white and Hispanic women in recent years, but Black women have by far seen the largest increase in maternal mortality. In 2022, around 253 Black women died from maternal causes in the United States.

Throughout the Common Era, Western Europe's population development fluctuated greatly. The population was very similar at the beginning and end of the first millennium, at around 25 million people. The largest decline in this period occurred in the sixth century, due to the Plague of Justinian, which the source claims to have killed around one third of the continent's population (although recent studies dispute this). Similarly, the population fell by almost 17 million throughout the 14th century, due to the Black Death.

Improvements in agriculture and infrastructure then saw population growth increase once more from the 15th century onwards, before the onset of the demographic transition saw a population boom throughout the 19th and 20th centuries.

For most of the world, throughout most of human history, the average life expectancy from birth was around 24. This figure fluctuated greatly depending on the time or region, and was higher than 24 in most individual years, but factors such as pandemics, famines, and conflicts caused regular spikes in mortality and reduced life expectancy. Child mortality The most significant difference between historical mortality rates and modern figures is that child and infant mortality was so high in pre-industrial times; before the introduction of vaccination, water treatment, and other medical knowledge or technologies, women would have around seven children throughout their lifetime, but around half of these would not make it to adulthood. Accurate, historical figures for infant mortality are difficult to ascertain, as it was so prevalent, it took place in the home, and was rarely recorded in censuses; however, figures from this source suggest that the rate was around 300 deaths per 1,000 live births in some years, meaning that almost one in three infants did not make it to their first birthday in certain periods. For those who survived to adolescence, they could expect to live into their forties or fifties on average. Modern figures It was not until the eradication of plague and improvements in housing and infrastructure in recent centuries where life expectancy began to rise in some parts of Europe, before industrialization and medical advances led to the onset of the demographic transition across the world. Today, global life expectancy from birth is roughly three times higher than in pre-industrial times, at almost 73 years. It is higher still in more demographically and economically developed countries; life expectancy is over 82 years in the three European countries shown, and over 84 in Japan. For the least developed countries, mostly found in Sub-Saharan Africa, life expectancy from birth can be as low as 53 years.