An infection caused by herpes simplex virus 1 (HSV-1) and usually associated with lesions on the lips, mouth, and face. HSV-1 is very contagious and is transmitted by direct contact with someone who is infected (even if lesions are not visible). Treatment cannot completely clear HSV-1 from the body, but antiviral therapy can shorten and prevent outbreaks and reduce the risk of transmission. People with weakened immune systems, such as people with HIV, are more likely to have lesions that spread to other parts of the body than people with healthy immune systems.