Overview
This lecture clarifies the difference between infection and disease, providing examples to illustrate when infection does not progress to disease.
Infection vs. Disease
- Infection occurs when a pathogen (disease-causing organism) invades or colonizes the body.
- Disease is the disruption of normal bodily functions with observable signs or symptoms.
- Not all infections result in disease; the two terms are not interchangeable.
Examples Illustrating Differences
- During the incubation period of an infectious disease, a person is infected but shows no symptoms (no disease yet).
- Some pathogens can infect a person for months, years, or decades before causing disease (e.g., shingles, HIV, C. diff).
- Shingles virus can remain in the body for decades after initial infection before disease symptoms appear.
- HIV can be present as an infection long before any symptoms or disease develop.
- Clostridioides difficile (C. diff) may colonize a person years before causing disease.
Key Terms & Definitions
- Infection — Invasion or colonization of the body by a pathogen.
- Disease — A state where normal body function is disrupted, leading to signs and symptoms.
- Pathogen — An organism capable of causing disease.
- Incubation Period — The time after infection but before symptoms appear.
- Homeostasis — The maintenance of a stable internal environment in the body.
Action Items / Next Steps
- Review textbook definitions of infection and disease.
- List more examples where infection does not immediately lead to disease.