Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
A primary infection is the initial infection caused by a pathogen entering and establishing itself in a host. It often paves the way for secondary infections by weakening the immune system.
5 Must Know Facts For Your Next Test
Primary infections are typically more severe because the immune system has not yet mounted a response.
Common examples of primary infections include influenza, tuberculosis, and HIV.
The site of entry for a primary infection can influence its severity and spread.
Primary infections can lead to chronic conditions if not properly treated.
Vaccinations are designed to prevent primary infections by preparing the immune system.
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Related terms
Secondary Infection: An infection that occurs during or after treatment of another pre-existing infection.