Which of the following is NOT typically listed as a major issue in medical ecology?

• A. Occurrence
• B. Susceptibility
• C. Source of disease
• D. Vaccine cold chain maintenance

Answer: (D)

In medical ecology, the major issues revolve around how often a disease occurs in a population, who is susceptible to infection, and where the pathogen originates or persists. Occurrence reflects the frequency and patterns of disease over time and space. Susceptibility involves host-related factors such as age, immune status, genetics, and comorbidities that affect risk. The source of disease points to reservoirs, vectors, or environmental sources that sustain the pathogen and enable transmission. Vaccine cold chain maintenance, while crucial for ensuring vaccine effectiveness, falls under vaccine logistics and program management rather than the ecological interactions among hosts, pathogens, and the environment. Therefore, it is not typically listed as a major issue in medical ecology.