Final answer:
Cold sores on the lips are caused by the Herpes simplex virus (HSV), specifically HSV-1. The virus is highly contagious and can remain dormant in the body, with the potential for reactivation and recurrent episodes.
Step-by-step explanation:
The medical assistant should identify that Herpes simplex virus (HSV), specifically HSV-1, causes cold sores on the lips. Cold sores, also known as fever blisters, usually appear on or around the lips and can occasionally appear on the face. These are red, fluid-filled blisters that are highly contagious even when sores are not necessarily visible. After the initial infection, the virus remains dormant in the body and can reactivate, causing recurrent episodes triggered by factors like stress or certain environmental conditions. Although there is no cure for herpes simplex virus, treatments such as antiviral medications can help manage outbreaks and reduce symptoms.