Spreading

Spreading refers to the process by which something extends its presence through space or among individuals, through transmission, diffusion, or propagation. It can describe the movement of tangible substances, biological agents, information, or abstract effects such as influence or risk.

In biology and medicine, spreading commonly refers to how diseases or parasites move through populations. Transmission may be direct, such as physical contact, or indirect, via airborne particles, contaminated surfaces, or vectors like mosquitoes. The rate of spread is influenced by contact patterns, infectiousness, and susceptibility, and is often summarized by measures such as the basic reproduction number R0 and the generation time.

In physics and ecology, spreading can describe diffusion of substances from regions of higher concentration toward lower concentration, or the dispersal of organisms across habitats. In ecology, an introduced species can spread, creating an invasion front that depends on dispersal ability and environmental resistance.

In information and social contexts, spreading refers to how ideas, behaviors, or memes propagate through networks. Models of diffusion of innovations and social contagion examine thresholds, clustering, and virality, while real-world spread is influenced by attention, incentives, and network structure.

In modeling, spreading is studied with differential equations, stochastic processes, networks, and spatial models. Data on case counts, contact networks, page views, or sensor readings are used to estimate spread rate, focal points, and eventual reach.

Examples include the geographic expansion of an infectious outbreak, wildfire spread, and the viral spread of a video or rumor online.