Herpes simplex is the common virus responsible for fever blisters or cold sores. This virus is primarily classified into two types: HSV-1 and HSV-2, with HSV-1 being the most common cause of oral herpes, which manifests as these blisters. Once the virus infects a person, it remains dormant in the body and can reactivate during times of stress, illness, or weakened immunity, leading to periodic outbreaks of fever blisters.
The other viruses mentioned serve different roles and are not linked to cold sores. Varicella is responsible for chickenpox and shingles, while influenza is a virus that causes the seasonal flu. HIV, or Human Immunodeficiency Virus, affects the immune system and is unrelated to cold sore outbreaks. Understanding the specific type of herpes virus involved helps in both the treatment and management of these outbreaks.