Smallpox: Humanity's Greatest Victory Over Disease

What Was Smallpox?

Smallpox was a devastating infectious disease caused by the variola virus. It existed in two forms: variola major (more severe, ~30% fatality) and variola minor (~1% fatality).[1] The disease spread through respiratory droplets and contact with skin lesions or contaminated materials.

Smallpox caused a distinctive rash that progressed from flat red spots to raised bumps, then fluid-filled blisters, and finally pus-filled pustules that crusted over. Survivors were often left with disfiguring scars; many were blinded.

A Long History of Terror

Smallpox plagued humanity for at least 3,000 years. Evidence of smallpox-like rashes has been found on Egyptian mummies, including Ramses V (died 1157 BCE). The disease devastated populations across Asia, Europe, and Africa for millennia.

When European colonizers brought smallpox to the Americas in the 15th and 16th centuries, the results were catastrophic. Indigenous populations, with no immunity, were decimated. Some historians estimate that 90% of the indigenous population died, largely from infectious diseases led by smallpox. It was among the most devastating epidemiological disasters in human history.

In 18th century Europe, smallpox killed an estimated 400,000 people annually and was responsible for a third of all blindness. Even into the 20th century, it killed an estimated 300 million people.[2]

The Birth of Vaccination

The concept of immunization against smallpox predates modern medicine. In China and India, variolation, deliberately exposing people to material from mild smallpox cases, had been practiced for centuries. The procedure was risky but effective, reducing mortality significantly.

The breakthrough came in 1796 when English physician Edward Jenner observed that milkmaids who had contracted cowpox, a mild disease, seemed immune to smallpox.[4] He tested his hypothesis by inoculating 8-year-old James Phipps with material from a cowpox lesion on a milkmaid's hand. Six weeks later, Jenner exposed the boy to smallpox. He didn't develop the disease.

Jenner called his technique vaccination (from "vacca," Latin for cow). It was safer than variolation and became the foundation for modern immunology. Within years, vaccination spread across Europe and the Americas.

"The annihilation of the smallpox, the most dreadful scourge of the human species, must be the final result of this practice."

- Edward Jenner, 1801

The Eradication Campaign

By the 20th century, smallpox had been eliminated from wealthy countries through vaccination. But it continued to devastate developing nations. In 1967, the World Health Organization launched the Intensified Smallpox Eradication Programme.

The campaign faced enormous challenges: reaching remote populations, maintaining vaccine potency in tropical heat, overcoming political instability, and tracking cases in countries with minimal health infrastructure. Success required innovation:

• Bifurcated needle: A simple, cheap tool that reduced vaccine waste 4-fold
• Freeze-dried vaccine: Stable without refrigeration in tropical climates
• Ring vaccination: Vaccinating contacts of cases rather than entire populations
• Surveillance-containment: Aggressively hunting down every case

The last natural case of variola major occurred in Bangladesh in October 1975. The last natural case of variola minor occurred in Somalia in October 1977. On May 8, 1980, the World Health Assembly declared smallpox officially eradicated, the first (and still only) human disease to achieve this milestone.[1]

Key Figures

Lessons for Today

The eradication of smallpox offers crucial lessons:

• Eradication is possible: With political will, resources, and the right tools
• Innovation matters: Simple technologies like the bifurcated needle were game-changers
• Surveillance is key: Finding and containing cases is as important as vaccination
• Global cooperation works: Even Cold War rivals collaborated on eradication

Today, smallpox exists only in two WHO-authorized laboratories in the United States and Russia. Debates continue about whether these stocks should be destroyed. Meanwhile, the virus's potential use as a bioweapon remains a security concern, one reason why some countries maintain smallpox vaccine stockpiles.

The Only One?

Despite decades of effort, smallpox remains the only human disease ever eradicated. Polio is close, but challenges persist. Measles could theoretically be eradicated but vaccine hesitancy has caused resurgences.

Smallpox had unique characteristics favoring eradication: no animal reservoir, visible symptoms, one serotype, lifelong immunity from infection or vaccination. Other diseases are more complex. But the lesson stands: with sufficient commitment, even ancient scourges can be defeated.