History's Worst Pandemics

As human civilizations flourished, so did infectious disease. Large numbers of people living in close proximity to each other and to animals, often with poor sanitation and nutrition, provided fertile breeding grounds for disease. And new overseas trading routes spread the novel infections far and wide, creating the global pandemics.

Three of the deadliest pandemics in recorded history were caused by a single bacterium, Yersinia pestis, a fatal infection otherwise known as the plague.

Plague

The Plague of Justinian arrived in Constantinople, the capital of the Byzantine Empire, in 541 CE. The plague decimated Constantinople and spread like wildfire across Europe, Asia, North Africa and Arabia killing an estimated 30 to 50 million people, perhaps half of the world’s population. As to how the plague ended, the best guess is that the majority of people in a pandemic somehow survive, and those who survive have immunity.

It returned 800 years later. The Black Death, which hit Europe in 1347, claimed an astonishing 200 million lives in just four years. People still had no scientific understanding of contagion, but they knew that it had something to do with proximity. So the officials in the port city of Ragusa decided to keep newly arrived sailors in isolation until they could prove they weren’t sick. At first, sailors were held on their ships for 30 days, which became known in Venetian law as a trentino. As time went on, the Venetians increased the forced isolation to 40 days or a quarantino, the origin of the word quarantine and the start of its practice in the Western world.

The plague resurfaced roughly every 20 years from 1348 to 1665—40 outbreaks in 300 years. And with each new plague epidemic, 20 percent of the men, women and children living in the British capital were killed. By the early 1500s, England imposed the first laws to separate and isolate the sick.

The Great Plague of 1665 was the last and one of the worst of the centuries-long outbreaks, killing 100,000 Londoners in just seven months. All public entertainment was banned and victims were forcibly shut into their homes to prevent the spread of the disease. Red crosses were painted on their doors.

Smallpox

Smallpox was endemic to Europe, Asia and Arabia for centuries, a persistent menace that killed three out of ten people it infected and left the rest with pockmarked scars. The indigenous peoples of modern-day Mexico and the United States had zero natural immunity to smallpox and the virus cut them down by the tens of millions. There hasn’t been a kill off in human history to match what happened in the Americas—90 to 95 percent of the indigenous population wiped out over a century.

Centuries later, smallpox became the first virus epidemic to be ended by a vaccine. In the late 18th-century, a British doctor named Edward Jenner discovered that milkmaids infected with a milder virus called cowpox seemed immune to smallpox. Jenner famously inoculated his gardener’s 9-year-old son with cowpox and then exposed him to the smallpox virus with no ill effect.

In the early- to mid-19th century, cholera tore through England, killing tens of thousands. The prevailing scientific theory of the day said that the disease was spread by foul air known as a “miasma.” But a British doctor named John Snow suspected that the mysterious disease, which killed its victims within days of the first symptoms, lurked in London’s drinking water. While cholera has largely been eradicated in developed countries, it’s still a persistent killer in third-world countries lacking adequate sewage treatment and access to clean drinking water.

The Third Plague Pandemic happened in 1855. Starting in China and moving to India and Hong Kong, the bubonic plague claimed 15 million victims. Initially spread by fleas during a mining boom in Yunnan. India faced the most substantial casualties, and the epidemic was used as an excuse for repressive policies that sparked some revolt against the British. The pandemic was considered active until 1960 when cases dropped below a couple hundred.

1889: Russian Flu

The first significant flu pandemic started in Siberia and Kazakhstan, traveled to Moscow, and made its way into Finland and then Poland, where it moved into the rest of Europe. By the following year, it had crossed the ocean into North America and Africa. By the end of 1890, 360,000 had died.

1918: Spanish Flu

The avian-borne flu that resulted in 50 million deaths worldwide, the Spanish flu is theorized to have originated in China and been spread by Chinese laborers being transported by rail across Canada on their way to Europe. In North America, the flu first appeared in Kansas in early 1918 and was visible in Europe by spring. Wire service reports of a flu outbreak in Madrid in the spring of 1918 led to the pandemic being called the “Spanish flu.” By October, hundreds of thousands of Americans died and body storage scarcity hit crisis level. But the flu threat disappeared in the summer of 1919 when most of the infected had either developed immunities or died.

1957: Asian Flu

Starting in Hong Kong and spreading throughout China and then into the United States, the Asian flu became widespread in England where, over six months, 14,000 people died. A second wave followed in early 1958, causing an estimated total of about 1.1 million deaths globally, with 116,000 deaths in the United States alone. A vaccine was developed, effectively containing the pandemic.