What term describes the feature of a pathogen that helps it cause disease?

The term that describes a feature of a pathogen that aids in causing disease is "virulence factor." Virulence factors are specific components or characteristics that enhance a pathogen's ability to infect a host, evade the immune response, and cause damage. These can include toxins, enzymes, adhesion molecules, and other substances that enable pathogens to establish infection and contribute to the severity of disease.

For instance, in bacteria, virulence factors may allow them to adhere to host tissues, penetrate cells, or evade immune detection, thereby increasing their pathogenic potential. Understanding these factors is crucial in microbiology as it informs the development of treatments and vaccines to combat infections.

The other terms listed do not accurately capture this concept. Pathogenic trait may seem similar but is not the specific term used in microbiological contexts. The infectivity index is a measure of how easily a pathogen can be transmitted, rather than a characteristic that causes disease. Resistance marker typically refers to genes or traits that allow pathogens to resist antimicrobial treatments, not specifically features that contribute to disease causation.