Lessons from History
Learning Objectives
Students will be able to:
- Compare historical and recent pandemics using epidemiological concepts
- Identify patterns that repeat across different outbreaks
- Explain how scientific understanding has evolved
- Apply lessons learned to future preparedness
Major Respiratory Pandemics
| Pandemic | Years | Deaths | R0 |
|---|---|---|---|
| 1918 "Spanish" Flu | 1918-1920 | 50-100 million | 2-3 |
| SARS | 2002-2003 | 774 | 2-3 |
| H1N1 Swine Flu | 2009-2010 | 150-575,000 | 1.5 |
| COVID-19 | 2019-present | 7+ million | 2-3 (original) |
Comparing Three Pandemics
| Feature | 1918 Flu | SARS 2003 | COVID-19 |
|---|---|---|---|
| Pathogen | Influenza virus | Coronavirus | Coronavirus |
| R0 | 2-3 | 2-3 | 2-3 (original) |
| Main transmission | Droplet/aerosol | Droplet/aerosol | Aerosol |
| Vaccines available | No | No | Yes (rapid development) |
| Global travel | Ships, trains | Aircraft | Aircraft (widespread) |
| Contained? | Burned out | Yes, within months | Ongoing/endemic |
The St. Louis vs. Philadelphia Story
Philadelphia
Held Liberty Loan Parade on Sept 28, 1918 despite outbreak warnings.
Result: Massive spike in cases, overwhelmed hospitals, 12,000+ deaths
St. Louis
Closed schools, banned gatherings, acted early when cases appeared.
Result: Much lower peak, ~700 deaths
Same virus, same country, same time. Different responses, dramatically different outcomes.
Patterns Across History
- Initial denial/delay — "It won't be that bad"
- Science evolves during crisis — We learn huge amounts DURING pandemics
- Same mistakes repeated — Lifting restrictions too early, inconsistent measures
- Early action saves lives — St. Louis vs. Philadelphia
- Unequal impacts — Poor and crowded communities hit harder
- Memory fades — We forget lessons between pandemics
The Aerosol Recognition Timeline
It took 100 years to fully accept aerosol transmission:
| Era | Understanding |
|---|---|
| 1918 | "Fresh air" treatment used but mechanism unclear |
| 1930s-1950s | Focus shifts to "droplets" (3-6 feet rule) |
| 1960s | TB recognized as airborne |
| 2020 | COVID-19 forces aerosol recognition |
| 2021 | WHO finally acknowledges airborne transmission |
This is why ventilation and filtration matter so much!
Reflection: Lessons We Shouldn't Forget
- What's one thing we knew in 1918 that we forgot by 2020?
- What's one advantage we had in 2020 that didn't exist before?
- What THREE things should every school/building do to prepare for the next respiratory pandemic?
- What's one thing YOU personally learned in this unit that you'll remember?
Unit 4 Summary: What We Learned
Transmission
Many respiratory infections spread via aerosols in shared indoor air
R0
R > 1 means growth; small changes have big effects
Epidemic Math
Doubling time, epidemic curves, growth and decline phases
Investigation
Person, Place, Time; attack rates; identifying sources
Interventions
Swiss cheese model; ventilation + filtration + masks + vaccines
History
Patterns repeat; preparedness and early action save lives
Unit 4 Complete!
You now understand how respiratory infections spread, the math behind epidemics, how to investigate outbreaks, and what interventions work. Most importantly, you've learned that early action, ventilation, and layered protection can dramatically reduce disease spread.
If there's a new respiratory pandemic in 20 years, you'll know what to do!