The term Agent might also refer to chemical or physical causes of disease or injury.

• A. True
• B. False
• C. Not Applicable
• D. Rarely

Answer: (A)

In epidemiology, an agent is any factor that can cause disease or injury, not limited to microbes. The term is used in the agent–host–environment framework to identify the cause of illness. While infectious agents like bacteria and viruses are classic examples, chemical agents (toxins, pollutants, poisons) and physical agents (radiation, heat, trauma) can also initiate disease or injury. This broad view helps explain how a person can develop illness from nonbiological causes as well.

So, the statement is true because chemical or physical factors can act as the etiologic agents responsible for disease or injury, just as biological agents can. The other options don’t fit: it isn’t restricted to biological causes, so false would be inappropriate; not applicable and rarely imply the concept doesn’t apply, which isn’t correct given the clear role of nonbiological agents in health outcomes.