Pathogen life cycles, host invasion, zoonoses and transmission pathways

What this note covers

1. A life cycle links survival, reproduction and transmission
2. Invasion requires entry, establishment and host impact
3. Transmission routes determine effective interruption
4. Zoonoses link animal and human infection pathways
5. Pathogen success reflects trade-offs, not maximum harm
6. Causal pathway evidence needs time, controls and uncertainty

6 sections · 10 key terms & formulas · 6 common mistakes