host factor

Host factor (sometimes known as risk factor){{Cite web |date=2021-12-20 |title=Principles of Epidemiology {{!}} Lesson 1 - Section 8 |url=https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section8.html |access-date=2023-01-30 |website=www.cdc.gov |language=en-us}} is a medical term referring to the traits of an individual person or animal that affect susceptibility to disease, especially in comparison to other individuals.{{Cite web |title=Host factors |url=https://medical-dictionary.thefreedictionary.com/Host+factors |access-date=2023-01-30 |website=TheFreeDictionary.com}} The term arose in the context of infectious disease research, in contrast to "organism factors", such as the virulence and infectivity of a microbe. Host factors that may vary in a population and affect disease susceptibility can be innate or acquired.

Some examples:

• general health
• psychological characteristics and attitude
• nutritional state
• social ties
• previous exposure to the organism or related antigens
• haplotype or other specific genetic differences of immune function
• substance abuse
• race

The term is now used in oncology and many other medical contexts related to individual differences of disease vulnerability.