Temporal and spatial scales in epidemiological concepts

Area of Science:

• Epidemiology
• Ecology
• Pathogen dynamics

Background:

• Traditional epidemiological concepts lack defined temporal and spatial scales.
• Zoological, botanical, and theoretical epidemiology use varying epidemic definitions.
• Precise scales are crucial for hypothesis testing and ecological validity.

Purpose of the Study:

• To review traditional epidemiological concepts from ecological, cultural, and logical viewpoints.
• To propose criteria for identifying temporal and spatial scales in epidemiology.
• To introduce a unified definition of an epidemic incorporating space-time scales.

Main Methods:

• Ecological, cultural, and logical perspectives were used to review epidemiological concepts.
• Criteria for temporal and spatial scales were developed based on observational consistency and ecological validity.
• Pathogen persistence (absent, sporadic, endemic) was classified.

Main Results:

• Current epidemiological definitions often omit temporal and spatial scales.
• Proposed criteria ensure consistency of observation, considering host-pathogen life cycles and environmental factors.
• A novel definition of an epidemic is presented: an indicator variable reaching a statistically unusual value within an ecologically relevant space-time unit.

Conclusions:

• Incorporating defined temporal and spatial scales enhances epidemiological precision.
• The proposed epidemic definition promotes consistency across zoological, botanical, and theoretical epidemiology.
• While not directly altering modeling, revised hypotheses may impact model analyses.