All three contribute factors (disease determinants) that may increase or decrease the chance of developing disease.

• A. True
• B. False
• C. Sometimes
• D. Never

Answer: (A)

Disease risk is shaped by the interaction of three components: the host, the agent, and the environment. Each of these can tilt the probability of developing disease up or down, and they work together rather than in isolation. The host factors include things like immune status, age, genetics, and vaccination history—strong immunity can decrease risk, while immunosuppression can increase it. The agent factors involve characteristics such as virulence and infectious dose—less virulent strains or lower doses make disease less likely, whereas highly virulent agents can raise the chance of illness. The environmental factors cover exposure opportunities and transmission conditions—crowded living conditions, poor sanitation, or presence of vectors can raise risk, while good housing, sanitation, and vector control can reduce it. Because these determinants interact to influence exposure and susceptibility, the statement that all three contribute factors that may increase or decrease the chance of developing disease is true.