Calculator Inputs
Example Data Table
These sample rows show how different biology exposure settings can shift the final risk estimate.
| Scenario | Prevalence % | Contacts/hr | Hours | Mask % | ACH | Susceptibility | Estimated Risk |
|---|---|---|---|---|---|---|---|
| Outdoor short contact | 4 | 3 | 0.8 | 60 | 10 | 0.9 | 1.9% |
| Indoor classroom session | 7 | 6 | 2.0 | 40 | 4 | 1.0 | 15.7% |
| Busy clinic waiting room | 10 | 8 | 2.5 | 35 | 2 | 1.2 | 35.6% |
| High-density enclosed event | 14 | 10 | 4.0 | 20 | 1 | 1.3 | 68.4% |
Formula Used
Exposure load = contacts per hour × duration hours
Expected infectious contacts = exposure load × prevalence rate
Ventilation factor = max(0.20, 1 ÷ (1 + ACH ÷ 6))
Control modifier = (1 − mask reduction) × (1 − eye protection reduction) × (1 − hand hygiene × 0.25)
Environment modifier = pathogen factor × indoor factor × distance factor × density factor × ventilation factor
Biological modifier = (1 − immunity reduction) × susceptibility multiplier
Transmission load λ = expected infectious contacts × base transmission coefficient × environment modifier × control modifier × biological modifier
Infection probability = 1 − e−λ
This structure behaves like a Poisson-style hazard estimate. It is useful for comparing scenarios, controls, and assumptions in biology planning workflows.
How to Use This Calculator
- Enter a realistic prevalence estimate for the population you are assessing.
- Set your effective contact rate and total exposure duration.
- Adjust environmental inputs for indoor conditions, spacing, density, and ventilation.
- Enter the effectiveness of masks, eye protection, hygiene, and immunity.
- Choose a susceptibility multiplier if the host is more or less vulnerable than baseline.
- Click the calculate button to display the result above the form.
- Review the graph, modifiers, and category to compare safer and riskier scenarios.
- Use the CSV and PDF buttons to save your assumptions and results.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates a scenario-based infection probability using prevalence, exposure intensity, environment, protective measures, immunity, and host susceptibility. It is best for comparing relative risk across different biology settings.
2. Is this tool a medical diagnosis?
No. It does not detect disease, confirm infection, or replace medical evaluation. It is an educational model for structured risk thinking and scenario comparison.
3. Why does ventilation matter so much?
Better ventilation usually lowers airborne concentration and shortens persistence of infectious particles. In the calculator, higher ACH reduces the ventilation factor and lowers the final transmission load.
4. How should I choose the prevalence value?
Use the best available estimate for the exposed group or local setting. You can also test several prevalence levels to see how sensitive the final risk is to uncertain background infection rates.
5. Why is hand hygiene weighted less than masks?
This model treats hand hygiene as a partial modifier because many scenarios emphasize respiratory spread more strongly. You can still raise or lower that input to compare how route assumptions affect the outcome.
6. What does the susceptibility multiplier represent?
It adjusts biological vulnerability relative to a baseline host. Values above 1 raise risk, while values below 1 lower it. This lets you compare generalized population differences or experimental assumptions.
7. Can I use this for different pathogens?
Yes, as a relative model. Adjust the pathogen factor and base transmission coefficient to reflect stronger or weaker infectiousness. Results remain approximate and should be interpreted carefully.
8. Why does the graph rise over time?
Longer exposure increases cumulative transmission load. The graph visualizes that build-up, making it easier to see how much extra time under the same conditions can change the final probability.