Zoonotic spillover occurs when a pathogen jumps from an animal reservoir to humans.
Spillover Process
- Reservoir: Wildlife maintain the pathogen (bats, rodents, birds)
- Interface: Human-animal contact creates opportunities
- Spillover: Pathogen infects first human case
- Adaptation: Mutations may enable human-to-human spread
Key Factors
- Deforestation and habitat encroachment
- Wildlife trade and wet markets
- Agricultural intensification
- Climate change shifting species ranges
Pandemic Potential
Most spillovers are dead-ends. The danger is when the pathogen adapts for efficient human transmission (R₀ > 1).