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VaxVsBug - Environmental Hostility Method

Purpose

This document describes how environmental_hostility values are assigned in the app.

It is not a direct scientific metric imported from one official source. It is a comparative app model informed by epidemiological concepts and official disease documentation. This parameter is a simplified abstraction. It does not map directly to a single epidemiological quantity such as R0 or transmission rate, but is intended to approximate overall transmission pressure in a way that is comparable across diseases within the app. It can be loosely thought of as a normalized transmission-pressure proxy within the app.

What This Model Represents

environmental_hostility is meant to capture:

  • how strongly a disease tends to spread in the app's shared scenario
  • before vaccine protection reduces the risk

It is informed by:

  • transmission mode
  • spread potential
  • circulation or carriage context
  • outbreak behavior

It is not intended to represent:

  • annual incidence
  • lifetime risk
  • one official published number

To support comparison and interaction, these factors are intentionally collapsed into a single value. This simplifies the underlying dynamics and trades epidemiological detail for clarity and consistency across diseases.

Shared Scenario

The model assumes:

  • a modern society
  • the disease is circulating
  • community protection varies
  • the value reflects how hostile the disease environment becomes when protection is weak

Score Meaning

For the scored columns:

  • 1 = low
  • 3 = medium
  • 5 = very high

Scoring Rule

environmental_hostility is currently assigned in two steps:

  1. Score the disease on:

    • Spread potential
    • Circulation / carriage context
    • Outbreak behavior

  2. Convert the overall judgment into a bounded decimal value

This is not a strict mathematical formula. It is a structured comparative judgment. The scoring uses rough equal weighting as a starting point, with final values adjusted comparatively across diseases.

Use this rough mapping:

  • mostly 1s -> 0.05–0.15
  • low-to-mixed scores -> 0.15–0.30
  • mostly 3s -> 0.30–0.50
  • mostly 4s -> 0.50–0.70
  • near-maximum spread pressure -> 0.70+

The numeric ranges are chosen to preserve relative ordering and visible separation between diseases in the app, rather than to represent calibrated real-world probabilities.

Important:

  • assign values comparatively across the whole disease set
  • do not assign each disease in isolation
  • after scoring one disease, sanity-check it against nearby diseases in the table
  • assign environmental_hostility primarily from spread behavior; severity pressure may be used as a secondary calibration check or soft modifier so the final educational model remains honest

Slider Relation

The app uses environmental_hostility together with vaccine rate and vaccine effectiveness to calculate disease risk:

effective_infection_risk =
environmental_hostility x (1 - vaccination_rate x vaccine_effectiveness)

Where:

  • environmental_hostility is the baseline disease-pressure value in the app scenario
  • vaccination_rate is the community vaccine rate chosen with the slider
  • vaccine_effectiveness is the selected vaccine's protection value in the dataset

This means the slider does not change the disease's underlying hostility. It changes how much of that hostility is still able to produce infection.

Calibration Tables

Spread Pressure

Disease Transmission mode Spread potential (1–5) Circulation / carriage context (1–5) Outbreak behavior (1–5) Suggested hostility (1–5) Suggested environmental_hostility
Measles Airborne 5 4 5 5 0.75
Varicella Airborne + direct contact 4 4 4 4 0.55
Rotavirus Fecal-oral + environmental contamination 4 4 4 4 0.50
Hepatitis A Fecal-oral / contaminated food or water / close contact 4 2 4 3 0.25
Cholera Contaminated water or food / fecal-oral 3 2 5 3 0.28
Typhoid Contaminated water or food / fecal-oral 3 2 3 2 0.20
Pertussis Droplets / close respiratory spread 4 4 4 4 0.45
Influenza Droplets + close contact 4 5 3 4 0.45
Mumps Droplets / close contact 3 3 4 3 0.35
Rubella Airborne droplets 3 3 3 3 0.30
Diphtheria Droplets / close contact 3 2 4 3 0.30
Hepatitis B Blood and body fluids / perinatal / sexual 2 2 1 2 0.15
Pneumococcal Respiratory secretions + carriage 3 4 2 3 0.25
Polio Mainly fecal-oral 4 1 4 3 0.25
Hib Respiratory spread + carriage 3 2 2 2 0.18
Meningococcal Close / prolonged contact + carriage 2 2 3 2 0.12

Severity Pressure

Disease Acute severity (1–5) Hospitalization burden (1–5) Long-term harm (1–5) Fatality pressure (1–5) Severity pressure (1–5)
Measles 4 4 4 4 4
Varicella 2 2 2 2 2
Rotavirus 3 3 1 2 2
Hepatitis A 3 2 1 2 2
Cholera 5 4 1 4 4
Typhoid 4 4 2 3 3
Pertussis 3 4 2 3 3
Influenza 3 3 2 3 3
Mumps 2 2 3 1 2
Rubella 1 1 5 2 3
Diphtheria 4 4 4 4 4
Hepatitis B 2 2 5 4 4
Pneumococcal 3 4 4 4 4
Polio 3 2 5 3 4
Hib 4 4 4 3 4
Meningococcal 5 5 5 5 5

Interpretation Notes

  • Measles stands out as the strongest spread-pressure disease in this set.
  • Influenza is ambient and common, even if its outbreak dynamics differ from measles.
  • Hepatitis A has meaningful spread potential and outbreak behavior in the right sanitation or close-contact settings, but it does not carry the chronic long-term burden of hepatitis B.
  • Cholera has lower ambient circulation in the app's shared scenario, but can surge explosively in outbreaks when water, sanitation, and hygiene conditions fail.
  • Typhoid is less explosively outbreak-driven than cholera, but remains strongly tied to unsafe water, sanitation, and chronic human transmission.
  • Polio has high spread capability in the wrong environment, but low present-day circulation in many developed-world contexts.
  • Hepatitis B has lower ambient spread pressure in the app's shared scenario, but high long-term severity because chronic infection can lead to cirrhosis and liver cancer.
  • Meningococcal is severe, but not ambient in ordinary community spread the way measles or influenza are.
  • Pneumococcal, Hib, and Meningococcal are all influenced by carriage dynamics, which makes their spread pressure different from diseases that mainly present as obvious acute outbreaks.
  • Severity pressure is a separate judgment from spread pressure. It is grounded in acute illness, hospitalization, long-term sequelae, and fatality burden rather than transmissibility alone.

Severity Score Meaning

For the severity columns:

  • Acute severity
    • how serious the immediate illness can become
  • Hospitalization burden
    • how strongly the disease drives hospital-level illness
  • Long-term harm
    • disability, neurologic injury, hearing loss, amputation, chronic sequelae, or congenital harm
  • Fatality pressure
    • how strongly death is part of the disease burden
  • Severity pressure
    • the overall educational severity judgment for the app

Note:

  • Severity pressure is not the primary driver of environmental_hostility
  • it is intended as a secondary calibration check or soft modifier after spread-related scoring

Source Basis

These scores were inferred from official disease descriptions and public-health framing. They were not copied from one pre-existing hostility table.

Measles

Pertussis

Mumps

Rubella

Varicella

Polio

Hib

Influenza

Rotavirus

Hepatitis B

Hepatitis A

Cholera

Typhoid

Pneumococcal

Diphtheria

Meningococcal

Status

This is a calibration document for the open-source project.

Before updating app values, each row should still be reviewed against:

  • the disease's current app outcome model
  • the disease's current category and framing
  • whether the resulting chart gives an honest educational impression