Learning from three centuries of smallpox epidemics in London, UK

Date:
December 21, 2020
Source:
PLOS
Summary:
The current COVID-19 pandemic has caused a surge of interest in
the study of infectious disease transmission, and how control
measures could change the course of the pandemic. New research
examines the history of recorded smallpox epidemics in London.



FULL STORY ==========================================================================
The current COVID-19 pandemic has caused a surge of interest in the study
of infectious disease transmission, and how control measures could change
the course of the pandemic. New research published on 21st December 2020,
in the open access journal PLOS Biology, authored by Olga Krylova of
the Canadian Institute for Health Information and David Earn of McMaster University, examines the history of recorded smallpox epidemics in London.


========================================================================== Smallpox, one of the most devastating viral diseases ever to strike
humankind, is one of only two infectious diseases that have been
successfully eradicated by human efforts. 2020 marks the 40th anniversary
of smallpox eradication.

Krylova and Earn studied more than 13,000 weekly smallpox mortality
records, from 1664 to 1930, and found that the time between epidemics,
the size of the outbreaks, and even the season when the epidemics
occurred, changed over the centuries. They also annotated the smallpox
time series with major historical events, including the introduction
of various control interventions, before and after the discovery of a
vaccine in 1796.

The most common pre-vaccination intervention was variolation, which is
the practice of carefully controlled intentional infection with a small
dose of live virus, leading to immunity with lower risk of death than
from natural infection. Variolation has made news recently because it
has been suggested that "variolation" with COVID-19 might be occurring
as a beneficial side-effect of the use of masks.

The researchers digitized the weekly records published in the London
Bills of Mortality and the Registrar General's Weekly Returns. These
data provide a rare and valuable source for the study of ecology and
evolution of infectious diseases.

"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,"
says author David Earn, a professor of mathematics who specializes in
modelling of infectious disease transmission.

During the time period covered by the data, smallpox changed from
a terrifying and unavoidable danger to an easily preventable
infection. Introduction of better control measures, especially
vaccination, naturally led to decreased smallpox mortality and eventually eradication. Krylova and Earn present the first statistical analyses of
these extraordinary, weekly historical records.


========================================================================== Story Source: Materials provided by PLOS. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Olga Krylova, David J. D. Earn. Patterns of smallpox mortality
in London,
England, over three centuries. PLOS Biology, 2020; 18 (12):
e3000506 DOI: 10.1371/journal.pbio.3000506 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/12/201221140501.htm

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