Smallpox: Its History, Symptoms, and Eradication

Smallpox was a devastating disease that plagued human populations for thousands of years, causing widespread suffering and death. Its origins are believed to be over 3,000 years ago in India or Egypt. Smallpox affected all levels of society, from commoners to monarchs, claiming an estimated 400,000 European lives annually in the 18th century. This infectious disease significantly impacted global demographics, particularly in the New World, where it contributed to the deaths of an estimated 90-95% of the native population after its introduction by European explorers.

What Smallpox Was

Smallpox was an acute contagious disease caused by the variola virus. There were two main forms of the disease: variola major and variola minor. Variola major, the more common and severe form, had a mortality rate of about 30% in unvaccinated individuals, while variola minor was milder with a fatality rate of less than 1%.

Initial symptoms, appearing after an incubation period of 7 to 19 days, often resembled influenza, including high fever, malaise, headache, severe back pain, and sometimes vomiting. Two to three days later, a characteristic rash emerged, first on the face, hands, and forearms, then spreading to the trunk, palms, and soles. These lesions progressed uniformly from small red spots to raised bumps, then fluid-filled blisters with a central depression, and finally to pus-filled pustules.

The pustules would eventually scab over, and the scabs would fall off after about three weeks, leaving pitted scars. Historically, 65% to 80% of survivors were marked with these deep scars. Rare and severe forms of variola major included hemorrhagic smallpox, characterized by bleeding into mucous membranes and skin, and flat (or malignant) smallpox, where lesions remained soft and flat and did not progress to the pustular stage.

How Smallpox Spread

Smallpox primarily spread through direct and prolonged face-to-face contact, via infected aerosols and respiratory droplets released when an infected person coughed or sneezed. The virus could also be transmitted through direct contact with infected bodily fluids or contaminated objects like bedding or clothing. While less common, the virus could rarely spread through the air in enclosed settings like buildings or trains.

The incubation period, between exposure and first symptoms, typically ranged from 7 to 17 days, averaging 12 to 14 days. During this incubation period, an infected person generally felt fine and was not contagious. Contagiousness usually began with the onset of fever in the prodrome phase, but individuals became most contagious with the appearance of the rash and remained infectious until all the scabs had fallen off, which could take approximately three weeks.

The Global Effort to Eradicate Smallpox

The global effort to eradicate smallpox represents a significant achievement in public health. This endeavor gained significant momentum with the pioneering work of Edward Jenner in 1796. Jenner observed that milkmaids who had contracted cowpox, a milder disease, seemed protected from smallpox. He demonstrated that inoculating humans with live vaccinia virus (cowpox) could protect against smallpox, laying the foundation for modern vaccination.

Despite Jenner’s breakthrough, smallpox remained a global threat for many years due to challenges in vaccine production and distribution. In 1966, the World Health Assembly (WHO) voted to launch an intensified global eradication campaign. This program officially began in 1967, targeting smallpox in over 30 endemic countries.

The campaign employed various strategies, including mass vaccination in some areas, but a different approach, known as surveillance and containment, was adopted for developing countries. This involved active case-finding through house-to-house searches and offering rewards for reporting cases. Once a case was identified, “ring vaccination” was implemented, where all known and possible contacts of the infected individual were vaccinated to prevent further spread and contain the outbreak.

Enhanced technology, like the bifurcated needle, made vaccine delivery more efficient and cost-effective during this period. These coordinated efforts led to the last naturally occurring case of smallpox being diagnosed in Somalia in October 1977. On May 8, 1980, the 33rd World Health Assembly officially declared the world free of smallpox, marking its global eradication.

Smallpox in the Modern Era

The variola virus still exists in tightly controlled laboratory stockpiles. The World Health Organization (WHO) authorized the retention of these samples in two secure facilities: the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and the State Research Center of Virology and Biotechnology VECTOR in Koltsovo, Russia.

The existence of these remaining laboratory stockpiles continues to be a subject of debate among scientists and health officials. Proponents of destruction argue that retaining the virus poses a risk of accidental escape, while opponents believe the samples may still hold scientific value for developing new vaccines, antiviral drugs, and diagnostic tests. Advancements in genome science and genetic engineering also raise concerns about the potential for deliberate re-creation or misuse of the variola virus, even by non-state actors.

The risk of smallpox re-emergence, while very low, is not zero, leading to ongoing discussions about biosecurity and preparedness. International inspections of these laboratories are required every two years by the WHO Biosafety and Biosecurity Inspection Team to ensure secure containment. The global community continues to emphasize the need for improved diagnostics, vaccines, and therapeutics to respond to any potential outbreak or intentional release.

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