Which diffusion pattern exemplifies the spread of a disease through proximity from person to person?

• A. Hierarchical diffusion spreads via an ordered sequence.
• B. Stimulus diffusion involves adaptation.
• C. Contagious diffusion spreads through proximity from person to person.
• D. Relocation diffusion is diffusion via people moving.

Answer: (C)

Contagious diffusion centers on spread through close contact and physical proximity. When a disease moves from person to person, neighbors and nearby individuals are most likely to catch it first, so the outbreak expands outward in space from the initial case much like ripples from a stone. This pattern captures how infections commonly propagate in a community—through everyday interactions in classrooms, workplaces, and public spaces—before reaching farther areas as more people become contagious. By contrast, hierarchical diffusion travels through a network of places from more connected to less connected, stimulus diffusion involves spreading an underlying idea that changes in the process, and relocation diffusion spreads when people move and carry a disease to new locations. A nearby example is a flu outbreak spreading step by step through people in a neighborhood or school.