History of epidemics and Historical epidemics

4 April 2022

Julien Arino

Department of Mathematics & Data Science Nexus
University of Manitoba*

Canadian Centre for Disease Modelling
Canadian COVID-19 Mathematical Modelling Task Force
NSERC-PHAC EID Modelling Consortium (CANMOD, MfPH, OMNI/RÉUNIS)

* The University of Manitoba campuses are located on original lands of Anishinaabeg, Cree, Oji-Cree, Dakota and Dene peoples, and on the homeland of the Métis Nation.

Outline

  • Epidemiology
  • History of epidemics / Historical epidemics
  • Who, when and where
  • Fighting against infections
  • Mathematical Epidemiology
  • Computational epidemiology
  • Use of data in epidemiology

Epidemiology

Definition

Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in defined populations [Wikipedia]

Epidemiology is the study of how often diseases occur in different groups of people and why. Epidemiological information is used to plan and evaluate strategies to prevent illness and as a guide to the management of patients in whom disease has already developed [BMJ]

Etymology: the study of what is upon the people, derived from the Greek (upon, among), (people, district) and (study, word, discourse)

History of epidemics / Historical epidemics

Historical considerations

  • Epidemic outbreaks are among the earliest recorded events in history
  • Caveat: here, I barely discuss spatial aspects; this is done in Lecture 03 and Lecture 05. Spatiality does play a very important role, though

First known epidemics (from Wikipedia)

Event Date Location Disease Death toll (estimate)
Plague of Megiddo 1350 BCE Megiddo, land of Canaan Unknown Unknown
Plague of Athens 429–426 BCE Greece, Libya, Egypt, Ethiopia Possibly typhus, typhoid fever or VHF 75,000–100,000
412 BCE epidemic 412 BCE Greece, Roman Republic Possibly influenza Unknown
Antonine Plague 165–180 CE (possibly up to 190 CE) Roman Empire Possibly smallpox 5–10 million
Jian'an Plague 217 CE Han dynasty Possibly typhoid fever or VHF Unknown
Plague of Cyprian 250–266 CE Europe Possibly smallpox Unknown
Plague of Justinian (1st plague pandemic) 541–549 CE Europe and West Asia Bubonic plague 15–100 million (25–60% of population of Europe)
Roman Plague of 590 (1st plague pandemic) 590 CE Rome, Byzantine Empire Bubonic plague Unknown
Plague of Sheroe (1st plague pandemic) 627–628 CE Bilad al-Sham Bubonic plague 25,000+
Plague of Amwas (1st plague pandemic) 638–639 CE Byzantine Empire, West Asia, Africa Bubonic plague 25,000+
Plague of 664 (1st plague pandemic) 664–689 CE British Isles Bubonic plague Unknown
Plague of 698–701 (1st plague pandemic) 698–701 CE Byzantine Empire, West Asia, Syria, Mesopotamia Bubonic plague Unknown
735–737 Japanese smallpox epidemic 735–737 CE Japan Smallpox 2 million (approx. 1/3 of Japanese population)
Plague of 746–747 (1st plague pandemic) 746–747 CE Byzantine Empire, West Asia, Africa Bubonic plague Unknown

Who, when and where

Who, when and where

Recall part of the definition on Wikipedia

Epidemiology is the study and analysis of the distribution (who, when, and where)

Domain is terminologically heavy. A few pointers:

Who

  • Epidemiology typically used when dealing with humans, but sometimes also generically when an easy description is sought; e.g., plant disease epidemiology
  • Epizootic: denoting or relating to a disease that is temporarily prevalent and widespread in an animal population
  • Panzootic is like a pandemic for animals
  • One Health: considers health of humans, animals and their environment (including plants)

Incidence & Prevalence (when?)

Incidence: number of new cases in a population generated within a certain time period

Prevalence: number of cases of a disease at a single time point in a population

Epidemic curves

  • Used to record the occurrence of new cases as a function of time
  • When not too many cases, usually "individualised" (bar plots)
  • When number of cases is large, continuous curve

Some terminology for "where"

  • Epidemic: diseases that are visited upon a population
  • Pandemic: (will revisit this later in the course) epidemic that has spread across a large region, e.g., multiple continents or worldwide
  • Endemic: diseases that reside within a population
  • We don't say "panendemic"

Where: 1854 cholera outbreak

Cholera outbreak in Broad Street, London (UK)

Studied by John Snow

I found that nearly all the deaths had taken place within a short distance of the [Broad Street] pump

WHO pandemic (influenza) phases

Period Phase Description
Interpandemic 1 No animal influenza virus circulating among animals has been reported to cause infection in humans
2 Animal influenza virus circulating in domesticated or wild animals known to have caused infection in humans and therefore considered a specific potential pandemic threat
Pandemic alert 3 Animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in H2H transmission sufficient to sustain community-level outbreaks
4 Human-to-human transmission of an animal or human-animal influenza reassortant virus able to sustain community-level outbreaks has been verified
5 Same identified virus has caused sustained community-level outbreaks in at least 2 countries in 1 WHO region
Pandemic 6 In addition to criteria in Phase 5, same virus has caused sustained community-level outbreaks in at least 1 other country in another WHO region

Fighting against infections

Fighting against infections

Epidemiological information is used to plan and evaluate strategies to prevent illness and as a guide to the management of patients in whom disease has already developed

  • Preventing illness
    • Prophylactic measures
    • Vaccination
  • Managing illness
    • Prevention of further spread (e.g., in hospital)
    • Treatment

Immunisation

  • Smallpox first disease for which it was known
  • Mentioned in a 1549 Chinese book
  • China: powdered smallpox scabs blown up noses of the healthy; variolation-induced mortality not negligible (0.5-2%) but lower than normal (20%)
  • 1798: Edward Jenner introduces safer inoculation with cowpox (vaccination)
  • 1880s: Pasteur extends vaccination to chicken cholera and anthrax in animals and human rabies

At the time, herd immunity was not understood so this was for personal protection

Measles cases in the USA

Mathematical Epidemiology

Domain is quite old ..

.. but has only become a thing in recent years!

Daniel Bernoulli (1760)

  • BNF scan or pdf
  • Probably the first epidemic model
  • About petite vérole (smallpox) inoculation

Ross (early 1900)

  • On 20 August 1897, observed malaria parasites in the gut of a mosquito fed several days earlier on a malaria positive human
  • Nobel Prize for Medicine 1902
  • Started considering malaria eradication using mathematical models; for some history, read this 2012 paper

Kermack and McKendrick (1927+)

  • We spend a lot more time on this in Lecture 02
  • Groundbreaking set of papers starting in 1927
    • We will see one particular case, the most well known, but I point out here and point out in Lecture 02 that this is just the tip of the iceberg of their work

Some activity later, but not much until 1990s

  • In recent years, explosion
  • Since the beginning of COVID-19: just nuts..

Computational epidemiology

A more recent trend

Use of data in epidemiology

Has happened all along, undergoind a transformation

  • Epidemiology has long relied on data
  • Many developments in statistics originate there
  • Data has traditionally been better for chronic diseases than for infectious ones
  • Near-real-time surveillance of infectious diseases ongoing since the 1980s (e.g., Réseau Sentinelles)
  • SARS-CoV-1 saw the beginning of a move towards real-time emerging infectious disease data
  • With SARS-CoV-2, the system has really progressed a lot, both in terms of "citizen science" and governmental initiatives