Herpes virus is shed in huge numbers during outbreaks. It can also be shed in between outbreaks, when there are no signs or symptoms. Cold sores are caused by a common herpes virus. A closely related herpes simplex virus, HSV-2, causes most cases of genital herpes. But either HSV-1 or HSV-2 can cause a herpes sore on the face or genitals. Symptoms Herpes simplex: If a person has HSV-1, a bad sunburn can trigger a herpes simplex outbreak. Reproduction or republication strictly prohibited without prior written permission.