In the midst of a global pandemic, researchers are looking back in time at the one human disease that we successfully eradicated.
Even today, four decades after the public spread of smallpox, the disease is still seen as one of the biggest killers in history, giving more lives for more than a single infectious disease. any other, even plague and cholera.
In the 18th century, 400,000 Europeans died each year from smallpox. In London alone, more than 321,000 people died from the disease after 1664.
One-third of the survivors were left blind, and many more were destroyed by scallops.
“The current COVID-19 epidemic has shown increased interest in studying the spread of infectious diseases and how public health interventions may alter the course of the pandemic,” says David Earn, who models the transmission of infectious diseases at McMaster University in Ontario.
“Our aim was to report on and enable the weekly series of smallpox mortality in London and to identify historical events that may have affected the dynamics of smallpox over the centuries. “
For nearly 300 years, between 1664 and 1930, officers in London kept careful records of smallpox deaths. Digitizing more than 13,000 of these weekly reports, researchers have created a huge timeline of smallpox mortality and prevention, monitoring the movements of the virus in London and the ways in which it has been influenced by seasons, public health policies and historical events.
Over time, the results clearly show that better virus control led to fewer smallpox deaths.
Outbreaks appeared from time to time in earlier records, settling in a regular tide of diseases before 1770 as a raw type of smallpox called variolation.
It is only in 1810, at the same time that the much safer vaccine was introduced, that the data show a significant reduction in the extent of epilepsy, although outbreaks were more frequent and the more bizarre data. “
The first Vaccination Act in England in 1840 was a major pandemic in London in the 1830s, which eventually spread to Europe, providing free views to anyone who had calling for them and prohibiting more dangerous practices such as variolation. Only then did vaccination levels rise, with deaths falling.
Other effects such as the seasonal structure of epidemics and the seasonal timing of the cycles were more challenging to resolve, and the authors acknowledge that their data need further analysis.
That said, the timeline is, as they know, the longest weekly series of infectious disease mortality ever compiled. As such, it helps to show how a virus can go from being “a frightening and inevitable threat” – killing about one in three infected people – to cause of death very rare.
From killer to rare
In the years leading up to the last smallpox death in London, around 1934, very few deaths were reported from the virus.
“It is clear that smallpox control measures have been introduced – [inoculation] and later vaccinations – it has been eliminated, ”says Olga Krylova, who worked on the project while studying mathematics and statistics at McMaster.
“Our analysis also suggests that control measures and changes in public health policies have been increasingly used with changes in the incidence of epilepsy.”
Weekly trout mortality time series for London, England, 1664–1930. (Krylova and Earn, PLOS Biology, 2020)
Smallpox has a long and rich history, with mainstream thinking being linked to a rodent disease that made the leap in Africa a few thousand years ago. Over thousands of years, as the world became more global, this virus seems to have taken off, spread and spread along with human civilizations and their trade routes.
In medieval Europe, the virus often caused infectious diseases. The colony then spread it to Africa, Australia and North America.
Prior to the development of vaccines, people in Africa, India and China began to rely on change to control the spread of smallpox. This involved a small incision in the arm or leg, in which some of the smallpox virus was introduced, taken from the pustules or scabs of those who were already infected. .
The last amazing idea came to Europe in the 18th Century through trade with Turkey, and it was quickly taken up by doctors.
In 1796, a scientist named Edward Jenner discovered that smallpox, which is born from a virus similar to smallpox, could protect humans against infectious diseases of this infectious disease. When infected patients with this animal virus, it provided immunity in a safer, cheaper and more effective way than infestation with the human virus.
Before 1800, his work helped to produce the smallpox vaccine in England. Before 1840, inoculation was a thing of the past.
But that wasn’t the end of the smallpox. It was not until the late 19th century that scientists realized that immunization was not lifelong and that people had to be vaccinated again.
After that, a global campaign by the World Health Organization was able to successfully eradicate the virus in ten years. The last remaining samples are stored in the USA and Russia.
Through this long timeline, London was going through its own set of major cultural and historical changes. For example, the Industrial Revolution may have played a role in the epidemic of smallpox as urbanization and changed social demographics. Wars were also another way of spreading.
“Further research using mathematical models is needed to quantify the impact of historical interventions and events on the smallpox revolutions,” says Krylova.
This broad timeline hopes to allow scientists to do just that. By experiencing specific events and their effects, we may come to a better understanding of how infectious diseases can change over time, and what we can do to reverse them in the end. over there.
“The long history of recording smallpox mortality in London provides a unique opportunity to learn from the past about changing patterns in the spread of infectious diseases,” the authors conclude. .
Now is the time to dig into the data.
The study was published in Biology PLOS.