Three Centuries of Smallpox Records Offer Insights on Progression of Infectious Diseases

Smallpox deaths (blue) in London, England, 1664–1930, and the long-term trend of weekly births (red). (Credit: Olga Krylova and David J.D. Earn)

CN) — Smallpox, responsible for the deaths of millions over three millennia, was declared eradicated 40 years ago. As Covid-19 continues to plague the world, scientists on Monday revealed new insights into smallpox and how lessons learned from it helped guide modern medicine to a vaccine for the latest virus.

In a study published in the journal PLOS Biology, researchers Olga Krylova of the Canadian Institute for Health Information and David Earn of McMaster University in Canada, looked at historical records of smallpox outbreaks in London and how they relate to Covid-19.

“Our goal was to describe and make publicly available the weekly time series of smallpox mortality in London, and to identify historical events that might have influenced smallpox dynamics over the centuries,” Earn said in a statement.

The researchers examined some 13,000 smallpox mortality records from 1664 to 1930. What they discovered was that the outbreaks did not adhere to any sort of pattern.

“The time between epidemics, the size of the outbreaks and even the season when the epidemics occurred changed over the centuries,” the authors said.

In addition to being highly contagious, smallpox is frequently fatal. And those who managed to survive often suffered lifelong effects including blindness and disfigurement. According to the study, smallpox is believed to have killed more people than any other infectious disease, including up to 300 million worldwide in the 20th century alone.

Before the discovery of the smallpox vaccine in 1796, people subjected themselves to variolation, the act of introducing a small amount of a virus into a person’s system in order to gain immunity to it. The researchers note that the idea of variolation has reemerged with Covid-19 as a side-effect of wearing masks.

The scientists noted that “smallpox changed from a terrifying and unavoidable danger to an easily preventable infection.” They said vaccination helped to greatly decrease mortality numbers, along with “better control measures.”

In addition to recording the mortality records, the researchers also digitized the information so that other scientists and health professionals can more easily observe the historical data and use it in their own research.

“Our goal in this paper has been to describe — and make publicly available — the weekly time series of smallpox mortality in London, and to present information on a variety of historical factors that might have influenced smallpox dynamics over the centuries,” the authors wrote in the study.

Smallpox remains one of only two infectious diseases to have been eradicated by human efforts, and 2020 marked the 40th anniversary of the official demise of the disease.

The study comes after the U.S. Food and Drug Administration approved two Covid-19 vaccines from German company Pfizer and American biotech company Moderna.

More than 17 million Americans have been infected with the coronavirus, while over 310,000 have died from it.

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