Which of the following factors can contribute to a person being a host?

• A. exposure to physical, chemical, or nutritive agents
• B. being young or old
• C. poverty
• D. all above

Answer: (D)

Being a host means a person can harbor a pathogen and potentially transmit it. Susceptibility to infection is shaped by multiple interacting factors. Exposure to physical, chemical, or nutritive agents can damage barriers or alter defenses, increasing the chance that a pathogen can establish infection. Age matters because the very young have immature immune systems, and older adults may have waning immunity, making infections more likely or more severe. Poverty brings conditions such as crowded living, limited access to healthcare, poor nutrition, and greater exposure to environmental hazards, all of which raise risk and hinder prevention and treatment. Taken together, any of these factors can influence whether someone becomes a host, so all of these factors are contributing.