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Public Health, Epidemiology,�& Models

MMED 2024�Carl

https://doi.org/10.6084/m9.figshare.5038769.v3

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Goals

  • Define Public Health, Epidemiology, & Models
  • Discuss how they relate
  • Set up future sessions

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Practical!

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Public Health

Is:

  • guidelines for utilizing health facilities
  • coming up with health interventions for a group of people
  • cost and balances

Isn’t:

  • health at individual level
  • ???
  • ???

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Epidemiology

Is:

  • study of the behavior of diseases in a population
  • collection and filtering of data
  • study of the spread of disease

Isn’t:

  • about genetic diseases
  • invention of cures, treatments, etc
  • policy-making

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Modeling

Is:

  • an abstraction [mathematical, algorithmical, logical] of a process, system, etc.
  • estimation and prediction of a mathematical model
  • formal representation of a phenomenon

Isn’t:

  • an exact solution
  • an experiment
  • just mathematical

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Public Health

Is:

  • Focused on outcomes for whole group(s)
  • Conscious of tradeoffs / competing concerns
  • About what to *do*

Isn’t:

  • Individual diagnosis of a particular patient
  • “Do no harm” or generally about an easy “right way”
  • Only restricted to medical interventions

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Epidemiology

Is:

  • Creation, collection, & curation of data
  • about distribution & determinants of health-related states / events in populations
  • To identify causal factors of disease & non-disease

Isn’t:

  • Medicine, e.g. not treatment of patients
  • (Health) policy making or control activities
  • Expert in health-dependent states / measures / &c

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Modeling

Is:

  • Formal / rules-based description
  • Possible to use / implement as tool(s)
  • An abstraction / generalization across circumstances

Isn’t:

  • True or inclusive of all plausible phenomena
  • Necessarily a series of equations
  • An experiment

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How are they distinct?

How do they fit together?

Why should we care?

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Public�Health

Epidemiology

Modeling

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An example:

Ebola

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Ebola Virus Disease Overview

  • Symptoms initially flu-like: fever, aches, sore throat, but then developing into …
  • Hemorrhagic Fever, very high mortality
  • Several ebolaviruses: typically news re Zaire ebolavirus (ZEBOV); but may heard recently Sudan ebolavirus (SUDV) outbreak
  • Typical outbreaks start with spillover from wildlife (bats, NH primates) => home care-taking or healthcare w/ poor IPC leads to H2H transmission

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Ebola Virus Disease Overview

  • Historically: controlled by contact-tracing + careful IPC. Little evidence of transmission outside of direct contact with contaminated bodily fluids*
  • 2013-2016 West African outbreak first large scale incident => traditional control efforts seemingly overwhelmed => trialed vaccine rVSV-ZEBOV
  • Trial indicates exceptional individual protection from vaccination
  • …but rVSV-ZEBOV $$$ + challenging cold chain. Subsequent deployment in DRC outbreak with mixed success
  • Recent SUDV outbreak controlled w/o vaccination

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Epidemiology

Modeling

Public�Health

Ebola is terrifying => epidemic is crisis.

How much should / can we spend?

Before vs During epidemic, what policies should be enforced?

What infrastructure should we build / personnel should we train?

Should we stockpile vaccine or buy as needed?

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Public�Health

Modeling

Epidemiology

What are risky behaviors for transmission?

What is time course of infection / disease?

Can we detect Ebolaviruses in wildlife?

How well does the vaccine work at preventing infection? Disease?

What is the mortality rate? How many people have past exposure?

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Public�Health

Epidemiology

Modeling

How much vaccine, delivered when, prevents how many deaths?

Assuming next-generation distribution / timing, how long until X cases?

Given detection rate, how many infections when first death notified?

If response reduces R by Y, how many ETUs would be used?

If we distribute vaccine this vs that way, which do we think will prevent more cases?

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Public�Health

Epidemiology

Modeling

How well does the vaccine work at preventing infection? Disease?

How much vaccine, delivered when, prevents how many deaths?

Should we stockpile vaccine or buy as needed?

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Tension!

  • We can obtain some amount of vaccine - how much we have & when depending on whether we stockpile vs buy as needed
  • Vaccine works extremely well at preventing disease in individuals, so …
  • Targeted deployment to identified contacts prevents disease - but might not (incrementally) prevent onward transmission
  • Also: either way, spending on vaccine means not spending on other activities - what if we spend on contact tracing teams instead?

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Summary

  • Public Health, Epidemiology, & Models - different definitions, for different activities, serving different ends
  • Overlapping elements – typically need each other to “do well” – but worthwhile to remember distinctions
  • MMED aim: work on the intersection of the categories!

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Questions?

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This presentation is made available through a Creative Commons Attribution-Noncommercial license. Details of the license and permitted uses are available at� http://creativecommons.org/licenses/by/3.0/

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Attribution:

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Clinic on the Meaningful Modeling of Epidemiological Data

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