What Is the Difference Between Inflammation and Infection?

Inflammation and infection are terms used interchangeably in everyday language — but in medicine they describe distinct, though often related, biological processes. Understanding the difference is fundamental to understanding why antibiotics are not the solution for every illness, why some conditions cause redness and pain without any microorganism being present, and why the anti-inflammatory drugs work differently from antimicrobials.

Infection: The Presence Of A Microorganism

Infection is the invasion and multiplication of a pathogenic microorganism — bacterium, virus, fungus, parasite, or prion — in body tissues that are normally sterile, or in concentrations that exceed the body's immediate defenses.

Infection is defined by the presence of the pathogen. You cannot have an infection without a microorganism causing harm in the body. The bacteria causing a urinary tract infection, the influenza virus in airway cells, Candida causing a vaginal yeast infection, and Plasmodium in red blood cells during malaria are all infections.