Most of the time, when the herpes simplex virus or HSV infects a person, there are no symptoms.
It also usually moves from one person to another in the absence of symptoms, so it can therefore move through a population silently. Once in a while, though, it can cause symptoms, and typically those are in the form of skin and mucous membrane lesions. There are two types of herpes simplex viruses—HSV1 and HSV2—both of which are part of a larger family of enveloped double-stranded DNA viruses: the herpesviral family. Generally speaking, HSV1 tends to cause infections above the waist and HSV2 tends to cause infections below the waist, but there’s a lot of crossovers because both viruses can cause both types of infections.
HSV can sometimes involve the trunk, extremities, or head—a pattern that’s common among wrestlers because they have a lot of skin-to-skin contacts; and is therefore called herpes gladiatorum.
Finally, individuals with burn injuries or with atopic dermatitis can have really serious herpes infections in those areas, the latter even has a specific name—eczema herpeticum.
HSV can also affect the eye causing keratoconjunctivitis, which is inflammation of both the cornea and conjunctiva. In addition to symptoms of conjunctivitis which are pain, redness, tearing, and sensitivity to light, there can some classic signs of corneal involvement like blurry vision and a branching dendritic lesion which looks a bit like the tree-like dendrites of a neuron, which happens on the cornea itself, and this pattern is classic for herpes infection.
In rare cases, herpes viruses can spread to the central nervous system and cause meningitis or encephalitis, typically affecting the temporal lobe, in individuals of all ages. These can happen from a primary infection, but more commonly happen during reactivation when some of the viruses can escape into the bloodstream and reach the brain. When there is brain involvement, a lumbar puncture often has specific findings like an increase in red blood cells, an increase in white blood cells, and elevated protein levels. Some CT, MRI, and EEG changes can help to make the diagnosis.
HSV can also pass from a mother to a baby. Rather than causing a congenital infection while the fetus is in the uterus, most of the transmission happens at birth when the baby passes through infected maternal vaginal secretions during delivery. Neonatal HSV causes three different patterns of illness each occurring about ⅓ of the time.
HSV can cause unique symptoms in immunocompromised individuals who tend to have more frequent reactivation, more severe symptoms, and a wider range of symptoms, like lesions in the esophagus or lungs.
Herpes can usually be diagnosed based on how the skin or mucous membrane lesions look and can be confirmed with tests looking for viral DNA, like a polymerase chain reaction, an antibody response to the virus, or by growing the virus with viral culture. Although infections typically resolve without treatment within a couple of weeks, there are antiviral drugs like acyclovir, famciclovir, and valacyclovir that can be used topically or systemically to reduce pain and speed up healing. For recurring episodes, these treatments usually work best if taken when the prodrome starts; in other words, before the blisters develop, and high-dose intravenous antivirals may be given in more severe, or life-threatening situations.