Pandemics Through History

Malaria: Humanity's Oldest Scourge

Long before the great epidemics that struck suddenly and passed, malaria was killing people steadily, year after year. Caused by Plasmodium parasites and spread by the bite of Anopheles mosquitoes, it has afflicted humans since ancient times, shaping where people could live and helping to sap armies and empires. It remains one of the world's deadliest diseases, killing hundreds of thousands of people every year — most of them young children in Africa — though it is both preventable and curable.

Why it matters: Malaria may have killed more human beings over the ages than any other disease. Unlike the dramatic pandemics that flare and fade, it is a relentless, endemic killer that has been part of the human story from the beginning and still claims lives today.

The Plague of Athens

In the second year of the Peloponnesian War, a devastating epidemic swept through Athens, packed with refugees behind its walls. The historian Thucydides — who caught the disease and survived — left a vivid eyewitness account of its symptoms and of the social breakdown it caused. By its end the epidemic had killed upwards of a third of the population.

Why it matters: The Plague of Athens is the first epidemic in history described in careful, clinical detail, and it helped cripple Athens at the height of its power — a reminder of how disease can turn the course of history.

The Antonine Plague

Roman legions returning from campaigns in the East carried a terrible sickness — probably smallpox — back to the empire. The Antonine Plague raged for fifteen years, killing an estimated five million people across the Roman world, and struck again a generation later.

Why it matters: The Antonine Plague drained the manpower and economy of the Roman Empire at its height, weakening its armies and society and marking the beginning of Rome's long slide from its second-century peak.

The Plague of Cyprian

Beginning around 249 CE, a devastating pestilence swept the Roman Empire for some fifteen to twenty years. Named for St. Cyprian, the bishop of Carthage who described it, the plague at its height reportedly killed as many as 5,000 people a day in Rome. Its cause is uncertain — smallpox, a viral haemorrhagic fever, and pandemic influenza have all been suggested.

Why it matters: Striking during the chaotic 'Crisis of the Third Century,' the Plague of Cyprian drained the manpower of Rome's army and farms and deepened the turmoil that nearly tore the empire apart. Christians who nursed the sick won admiration and converts, helping the new faith spread.

The Plague of Justinian

The first recorded outbreak of bubonic plague erupted in the Byzantine Empire during the reign of Emperor Justinian, who caught the disease himself but survived. Spreading along trade routes from Egypt, it may have killed tens of millions of people around the Mediterranean over the following two centuries.

Why it matters: The Plague of Justinian was the first of history's three great bubonic plague pandemics. It shattered Justinian's dream of restoring the Roman Empire and reshaped the late-antique world.

The Black Death

Bubonic plague returned to Europe with catastrophic force, arriving on ships from the Black Sea and sweeping across the continent in just a few years. The Black Death killed an estimated one-third or more of Europe's population — tens of millions of people — in the worst pandemic in recorded history.

Why it matters: The Black Death transformed medieval Europe: labour shortages broke down the feudal order, wages rose, and the trauma reshaped religion, art, and society for generations. Few events have altered the course of history so profoundly.

Syphilis: The Great Pox

In 1495 a terrible new disease broke out among the soldiers of Charles VIII of France besieging Naples. As the mercenary armies dispersed, the 'great pox' — syphilis — spread across Europe within a few years. Sexually transmitted and far more virulent then than now, it caused disfiguring sores and could be fatal. Many historians link its sudden appearance to the return of Columbus's crews from the Americas, though the origin is debated.

Why it matters: Syphilis was the first great sexually transmitted epidemic of the modern era, a scourge that would haunt Europe for centuries until antibiotics — and a possible dark echo of the Columbian Exchange running in the opposite direction.

Smallpox and the Columbian Exchange

When Europeans reached the Americas, they brought diseases — above all smallpox — to which Indigenous peoples had no immunity. Epidemics raced ahead of the conquerors, killing a huge share of Native American populations, in places 90% or more, and helping a few hundred Spaniards topple great empires.

Why it matters: The disease catastrophe of the Columbian Exchange was one of the greatest demographic disasters in human history, and it made possible the European conquest and colonization of the Americas.

Cocoliztli: The Great Dying of Mexico

In 1545 a mysterious disease the Aztecs called cocoliztli ('pestilence') erupted in the highlands of Mexico, and struck again in 1576. Together the two epidemics killed an estimated 7 to 18 million people — a huge share of the surviving Indigenous population.

Why it matters: The cocoliztli epidemics were among the deadliest disease events in the Americas, compounding the smallpox catastrophe of the conquest and helping to depopulate central Mexico under Spanish rule.

How we know: The 1545 and 1576 death tolls come from colonial records; the cause is debated. A 2018 ancient-DNA study recovered Salmonella enterica (Paratyphi C) from victims' teeth, pointing to a form of enteric fever, while earlier researchers had proposed a viral haemorrhagic fever worsened by drought.

The Great Plague of London

The last great outbreak of bubonic plague in England struck London in 1665, killing roughly a quarter of the city's population within eighteen months. The wealthy fled to the countryside while the poor bore the brunt; the epidemic finally faded the following year, around the time of the Great Fire of London.

Why it matters: The Great Plague was the final major eruption of the centuries-long second plague pandemic in Britain, and the quarantine measures and bills of mortality it produced are milestones in the early history of public health record-keeping.

The Great Plague of Marseille

In May 1720 a merchant ship from the plague-ridden eastern Mediterranean, the Grand-Saint-Antoine, brought bubonic plague to the great French port of Marseille. Despite quarantine rules its cargo was unloaded, and the disease exploded through the city, killing about 1,000 people a day at its peak — roughly half of Marseille's population, and around 100,000 in the surrounding region.

Why it matters: The plague of Marseille was the last great outbreak of bubonic plague in Western Europe, the final wave of the centuries-long second pandemic that had begun with the Black Death — and a landmark case in the history of quarantine.

Variolation: The First Inoculation

Long before vaccination, people in Asia, Africa, and the Ottoman world practised 'variolation' — deliberately infecting a healthy person with material from a mild case of smallpox to induce lifelong immunity. In 1721 the practice reached the West on two fronts: Lady Mary Wortley Montagu, who had seen it in Constantinople, had children inoculated in England, while in Boston the enslaved African Onesimus described the technique to Cotton Mather, who promoted it during an outbreak.

Why it matters: Variolation was humanity's first deliberate method of preventing an epidemic disease. Risky but effective, it paved the way for Jenner's far safer vaccine — and its arrival in the West owed much to knowledge from Africa and the Islamic world.

Jenner and the First Vaccine

The English physician Edward Jenner tested a folk observation that milkmaids who caught mild cowpox never got smallpox. In 1796 he deliberately inoculated a boy with cowpox and then showed he was immune to smallpox. He called the method 'vaccination,' from the Latin vacca, for cow.

Why it matters: Jenner's vaccine was the first successful defence ever devised against an infectious disease, launching the science of immunization that would go on to save more lives than almost any other medical advance in history.

Cholera and the Age of Sanitation

As industrial cities swelled with crowded, filthy slums, cholera — a bacterial disease spread through water and food contaminated with human waste — erupted in a series of deadly pandemics that circled the globe from the 1810s onward. It could kill a healthy person within hours through catastrophic dehydration.

Why it matters: Tracing cholera to dirty water spurred the great sanitary reforms of the 19th century — clean water supplies and sewers — which remain the single most effective defence against the disease and a foundation of modern public health.

John Snow and the Birth of Epidemiology

When a violent cholera outbreak killed hundreds in London's Soho in 1854, the physician John Snow mapped the deaths and traced nearly all of them to a single public water pump on Broad Street. Persuading officials to remove the pump handle, he helped end the outbreak — and made his case that cholera spread through contaminated water, not 'bad air.'

Why it matters: Snow's Broad Street investigation is celebrated as the birth of modern epidemiology — the science of tracking disease through populations — and a foundation of evidence-based public health.

Germ Theory: Pasteur and Koch

For most of history, disease was blamed on bad air or imbalances in the body. In the 1860s the French chemist Louis Pasteur showed that microscopic organisms cause fermentation and disease, and developed vaccines for anthrax and rabies. In the 1880s the German physician Robert Koch proved that specific microbes cause specific diseases, identifying the bacteria behind anthrax, tuberculosis, and cholera.

Why it matters: Germ theory revolutionized medicine. Understanding that tiny living organisms cause infection made possible antiseptic surgery, vaccination, sanitation, and eventually antibiotics — the tools with which humanity finally began to fight back against epidemics.

Tuberculosis: The White Plague

Tuberculosis — the 'white plague' — was the leading cause of death in 19th-century Europe and North America, killing perhaps one in seven people. On 24 March 1882 Robert Koch announced to a Berlin audience that he had identified the bacterium that causes it, Mycobacterium tuberculosis, proving that TB was infectious rather than hereditary.

Why it matters: Koch's discovery transformed the fight against the deadliest disease of the age and is commemorated every year on World TB Day. Tuberculosis remains one of the world's top infectious killers even now.

The Russian Flu: The First Modern Pandemic

In 1889 a wave of influenza spread out of Central Asia and swept the globe in a matter of months, carried along the new networks of railways and steamships. The 'Russian flu' reached across Europe and the Atlantic to the Americas, killing about a million people and striking down key workers and public figures.

Why it matters: Often called the first modern pandemic, the Russian flu showed how the railways, steamships, and telegraphs of the industrial age could carry a disease around the world faster than ever before — the pattern every later pandemic would follow.

The Cause of Plague Revealed

As a new plague pandemic spread out of Asia, scientists finally identified the culprit behind history's great plagues: the bacterium Yersinia pestis, carried by fleas that live on rats and other rodents. The mystery that had terrified humanity for over a thousand years was solved.

Why it matters: Understanding that plague is a flea-borne bacterial infection at last explained the Justinianic Plague and the Black Death — and today, caught early, plague is a treatable disease cured with antibiotics rather than a death sentence.

Malaria and the Mosquito

For millennia malaria's cause was a mystery — its very name means 'bad air.' On 20 August 1897, working in India, the British doctor Ronald Ross found malaria parasites inside a mosquito that had fed on an infected patient, proving that the disease is spread by mosquito bites. He won the Nobel Prize in 1902.

Why it matters: Ross's discovery — alongside Walter Reed's work on yellow fever — showed that insects could transmit disease, opening the way to fight malaria and other scourges by controlling the mosquitoes that carry them.

Yellow Fever and the Mosquito

Yellow fever terrified port cities and doomed early attempts to build the Panama Canal. In 1900 a U.S. Army board led by Major Walter Reed, testing the theory of the Cuban doctor Carlos Finlay, proved through human experiments that mosquitoes transmit the disease. Mosquito-control campaigns then swiftly cleared yellow fever from Havana and, later, the Panama Canal Zone.

Why it matters: Confirming the mosquito as the carrier of yellow fever saved countless lives and made possible the completion of the Panama Canal. It was a landmark in the new science of controlling disease by controlling its insect vectors.

The 1918 Influenza Pandemic

As the First World War ended, a ferocious strain of H1N1 influenza swept the world in successive waves. Spread by wartime troop movements and censored by governments (giving it the misleading name 'Spanish flu'), it infected about a third of the global population and killed at least 50 million people — unusually, many of them young and healthy adults.

Why it matters: The 1918 pandemic was the deadliest of the 20th century, killing more people than the war that helped spread it, and it remains the benchmark against which modern pandemic preparedness is measured.

Penicillin and the Antibiotic Era

In 1928 the Scottish bacteriologist Alexander Fleming returned to his London lab to find that a mould had contaminated a bacterial culture and killed it. The mould, Penicillium, yielded the first true antibiotic — penicillin. Developed into a usable drug by Howard Florey and Ernst Chain in the early 1940s, it began saving lives during the Second World War.

Why it matters: Antibiotics gave humanity, for the first time, a reliable cure for the bacterial infections that had killed for all of history — from plague and tuberculosis to infected wounds. Fleming, Florey, and Chain shared the 1945 Nobel Prize.

Polio and the Vaccine

In the first half of the 20th century, poliomyelitis became a terror of the summer, striking mainly children under five and leaving many with irreversible paralysis; some could breathe only inside mechanical 'iron lungs.' Safe and effective vaccines introduced from the 1950s brought the epidemics under control, and a global eradication campaign launched in 1988 has since cut polio cases by more than 99%, from an estimated 350,000 a year to a mere handful.

Why it matters: Polio showed the power of vaccines to conquer a feared disease within a generation. Its near-elimination is one of the great public-health achievements in history — poised to make it only the second human disease, after smallpox, ever to be wiped out.

The Asian and Hong Kong Flu Pandemics

Two influenza pandemics struck in the mid-20th century. In 1957 a new H2N2 virus — the 'Asian flu' — emerged in East Asia and spread worldwide, killing over a million people. In 1968 a related H3N2 virus, the 'Hong Kong flu,' did much the same. Faster vaccine production and antibiotics for secondary infections helped keep their tolls well below that of 1918.

Why it matters: The 1957 and 1968 pandemics were reminders that influenza remains a recurring global threat, each new strain capable of circling the planet. They spurred the international influenza surveillance and vaccine systems that still guard against the next flu pandemic.

Measles and the Vaccine

Measles is one of the most contagious diseases known, and for most of history it was a near-universal disease of childhood that killed millions. Before a vaccine, major epidemics every few years caused an estimated 2.6 million deaths a year worldwide. A successful vaccine, licensed in 1963, and decades of immunization have since cut measles deaths dramatically.

Why it matters: The measles vaccine is one of the great life-savers of modern medicine — the WHO estimates vaccination prevented tens of millions of deaths in recent decades. Yet measles surges wherever vaccination coverage falls, a reminder that suppressed diseases can return.

The Eradication of Smallpox

Smallpox had killed hundreds of millions of people across history. Beginning in 1967, the World Health Organization led a global campaign of vaccination and case-tracking to hunt down every last outbreak. The final natural case occurred in 1977, and in 1980 the WHO declared smallpox eradicated.

Why it matters: Smallpox is the only human disease ever deliberately wiped from the face of the Earth — arguably the single greatest achievement in the history of public health, and proof that a pandemic disease can be defeated.

HIV/AIDS

In 1981 U.S. doctors reported clusters of rare infections in previously healthy young men — the first recognized cases of what became known as AIDS, caused by the human immunodeficiency virus (HIV). The virus spread into a global pandemic that has infected more than 80 million people and killed tens of millions.

Why it matters: HIV/AIDS reshaped medicine, activism, and society. Once a near-certain death sentence, it became — through antiretroviral drugs — a manageable chronic condition, one of modern medicine's hardest-won victories, though it remains a global challenge.

SARS: The First Epidemic of the 21st Century

In late 2002 a deadly new respiratory disease emerged in southern China. Caused by a coronavirus, SARS — severe acute respiratory syndrome — spread to some thirty countries in early 2003 via air travel, infecting around 8,000 people and killing about 800, roughly one in ten. An unprecedented global response contained it within months.

Why it matters: SARS was the first new epidemic disease of the 21st century and a warning of the danger of coronaviruses jumping from animals to humans. The swift international cooperation that stopped it — and the lessons it taught — would shape the response to COVID-19 two decades later.

The 2009 Swine Flu Pandemic

In 2009 a new H1N1 influenza virus — a 'swine flu' combining pig, bird, and human strains — emerged in North America and spread worldwide within weeks, prompting the WHO to declare the first flu pandemic in over 40 years. Unusually, it hit children and young adults hardest while largely sparing the elderly, who retained some immunity from older H1N1 strains. Global deaths were estimated in the hundreds of thousands.

Why it matters: The 2009 pandemic was the first influenza pandemic of the 21st century and the first to unfold under modern real-time genetic surveillance. It tested — and exposed gaps in — the world's pandemic-preparedness plans.

The West Africa Ebola Epidemic

In 2014 the largest Ebola outbreak in history erupted in West Africa, spreading through Guinea, Liberia, and Sierra Leone. The virus, which causes a severe and often fatal haemorrhagic fever, infected more than 28,000 people and killed over 11,000 before the epidemic was declared over in 2016. Weak health systems and a slow initial response let it spiral.

Why it matters: The West African Ebola epidemic exposed the fragility of global health defences and galvanized reform. It also spurred the development of an effective Ebola vaccine, turning one of the world's most feared diseases into a preventable one.

COVID-19

A novel coronavirus, SARS-CoV-2, emerged in late 2019 and spread around the world within months. In March 2020 the WHO declared a pandemic; societies locked down, and the disease killed millions. In a historic scientific feat, safe and effective vaccines — including new mRNA vaccines — were developed and deployed within a year.

Why it matters: COVID-19 was the first global pandemic of the hyper-connected 21st century, upending economies and daily life worldwide. Its rapid vaccine development marked a new era in the age-old struggle between humanity and infectious disease.

Mpox Goes Global

In 2022 mpox (formerly called monkeypox), a virus long confined mainly to parts of Africa, spread rapidly around the world for the first time. The WHO declared a global health emergency in July 2022; by the time it was lifted in 2023, more than 87,000 cases had been reported across some 110 countries. Targeted vaccination and behaviour change helped bring it under control.

Why it matters: The 2022 mpox emergency showed how a once-localized disease can go global in a connected world — and how quickly vaccines and public-health action can respond — even as it drew attention to the neglect of diseases in the regions where mpox had long circulated.