Herpes simplex is a viral disease caused by both herpes simplex virus 1(HSV-1) and herpes simplex virus 2 (HSV-2). Infection with the herpes virus iscategorized into one of several distinct disorders based on the site ofinfection. Oral herpes, the visible symptoms of which arecolloquially called cold sores,infects the face and mouth. Oral herpes is the most common form of infection. Genitalherpes, commonly known simply as herpes,is the second most common form of herpes. Other disorders such as herpeticwhitlow, herpes gladiatorum, ocular herpes (keratitis),cerebral herpes infection encephalitis, Mollaret's meningitis, neonatal herpes, and possibly Bell'spalsy are all caused by herpes simplex viruses.
Herpes viruses cycle between periods of active disease presenting asblisters containing infectious virus particles that last 2–21 days, followed by a remission period, during which the soresdisappear. Genital herpes, however, is often asymptomatic,though viral shedding may still occur. After initialinfection, the viruses move to sensorynerves, where they reside as life long, latentviruses. Causes of recurrence are uncertain, though some potential triggershave been identified. Over time, episodes of active disease reduce in frequencyand severity.
Herpes simplex is most easily transmitted by direct contact with a lesionor the body fluid of an infected individual. Transmission may also occurthrough skin-to-skin contact during periods of asymptomatic shedding. Barrierprotection methods are the most reliable method of preventing transmission ofherpes, but they merely reduce rather than eliminate risk. Oral herpes iseasily diagnosed if the patient presents with visible sores or ulcers. Earlystages of orofacial herpes and genital herpes are harder to diagnose;laboratory testing is usually required. Twenty percent of the U.S. populationhas antibodies to HSV-2, although not all of them have a history of genitallesions.
There is no cure for herpes. Once infected, the virus remains in the bodyfor life. However, after several years, some people will become perpetually asymptomaticand will no longer experience outbreaks, though they may still be contagious toothers. Vaccines are in clinical trials but have not demonstratedeffectiveness. Treatments can reduce viral reproduction and shedding, preventthe virus from entering the skin, and alleviate the severity of symptomaticepisodes.
Herpes simplex should not be confused with conditions caused by other virusesin the herpesviridaefamily such as herpes zoster, which is a viral disease caused by varicella zoster virus. There is also apossibility of confusion with "hand, foot and mouth disease" due toapparition of lesions on the skin
Signs and Symptoms
HSV infection causes several distinct medical disorders. Common infection of the skin ormucosa may affect the face and mouth (orofacial herpes), genitalia (genitalherpes), or hands (herpes whitlow). More serious disorders occur when the virusinfects and damages the eye (herpes keratitis), or invades the central nervoussystem, damaging the brain (herpes encephalitis). Patients with immature orsuppressed immune systems, such as newborns, transplant recipients, or AIDSpatients are prone to severe complications from HSV infections. HSV infectionhas also been associated with cognitive deficits of bipolardisorder, and Alzheimer's disease, although this is oftendependent on the genetics of the infected person.
There is a single report of a systemic infection with HSV-2, where a healthy28-year old woman with a healthy immune system died 12 days after contractingthe virus.
In all cases HSV is never removed from the body by the immunesystem. Following a primary infection, the virus enters the nerves at thesite of primary infection, migrates to the cell bodyof the neuron, and becomes latent in the ganglion. As aresult of primary infection, the body produces antibodies to the particulartype of HSV involved, preventing a subsequent infection of that type at adifferent site. In HSV-1 infected individuals, seroconversion after an oral infection will prevent additional HSV-1 infections such aswhitlow, genital herpes, and keratitis. Prior HSV-1 seroconversion seems toreduce the symptoms of a later HSV-2 infection, although HSV-2 can still becontracted. Most indications are that an HSV-2 infection contracted prior toHSV-1 seroconversion will also immunize that person against HSV-1 infection.