Herpes

Herpes simplex, often known simply as herpes, is a viral infection caused by the herpes simplex virus. Herpes infections are categorized by the area of the body that is infected. The two major types of herpes are oral herpes and genital herpes, though other forms also exist.
Oral herpes involves the face or mouth. It may result in small blisters in groups, often called cold sores or fever blisters, or may just cause a sore throat. Genital herpes involves the genitalia. It may have minimal symptoms or form blisters that break open and result in small ulcers. These typically heal over two to four weeks. Tingling or shooting pains may occur before the blisters appear.
Herpes cycles between periods of active disease followed by periods without symptoms. The first episode is often more severe and may be associated with fever, muscle pains, swollen lymph nodes and headaches. Over time, episodes of active disease decrease in frequency and severity.
Herpetic whitlow typically involves the fingers or thumb, herpes simplex keratitis involves the eye, herpesviral encephalitis involves the brain, and neonatal herpes involves any part of the body of a newborn, among others.
There are two types of herpes simplex virus, type 1 and type 2. HSV-1 more commonly causes infections around the mouth while HSV-2 more commonly causes genital infections. They are transmitted by direct contact with body fluids or lesions of an infected individual. Transmission may still occur when symptoms are not present. Genital herpes is classified as a sexually transmitted infection. It may be spread to an infant during childbirth. After infection, the viruses are transported along sensory nerves to the nerve cell bodies, where they reside lifelong. Causes of recurrence may include decreased immune function, stress, and sunlight exposure. Oral and genital herpes is usually diagnosed based on the presenting symptoms. The diagnosis may be confirmed by viral culture or detecting herpes DNA in fluid from blisters. Testing the blood for antibodies against the virus can confirm a previous infection but will be negative in new infections.
The most effective method of avoiding genital infections is by avoiding vaginal, oral, manual, and anal sex. Condom use decreases the risk. Daily antiviral medication taken by someone who has the infection can also reduce spread. There is no available vaccine and once infected, there is no cure. Paracetamol and topical lidocaine may be used to help with the symptoms. Treatments with antiviral medication such as aciclovir or valaciclovir can lessen the severity of symptomatic episodes.
Worldwide rates of either HSV-1 or HSV-2 are between 60% and 95% in adults. HSV-1 is usually acquired during childhood. Since there is no cure for either HSV-1 or HSV-2, rates of both inherently increase as people age. Rates of HSV-1 are between 70% and 80% in populations of low socioeconomic status and 40% to 60% in populations of improved socioeconomic status. An estimated 536 million people worldwide were infected with HSV-2 as of 2003 with greater rates among women and those in the developing world. Most people with HSV-2 do not realize that they are infected.

Etymology

The name is from herpēs, which is related to the meaning 'to creep', referring to spreading blisters. The name does not refer to latency.

Signs and symptoms

HSV infection causes several distinct medical disorders. Common infection of the skin or mucosa may affect the face and mouth, genitalia, or hands. More serious disorders occur when the virus infects and damages the eye, or invades the central nervous system, damaging the brain. People with immature or suppressed immune systems, such as newborns, transplant recipients, or people with AIDS, are prone to severe complications from HSV infections. HSV infection has also been associated with cognitive deficits of bipolar disorder, and Alzheimer's disease, although this is often dependent on the genetics of the infected person.
In all cases, HSV is never removed from the body by the immune system. Following a primary infection, the virus enters the nerves at the site of primary infection, migrates to the cell body of the neuron, and becomes latent in the ganglion. As a result of primary infection, the body produces antibodies to the particular type of HSV involved, which can help reduce the odds of subsequent infection of that type at a different site. In HSV-1-infected individuals, seroconversion after an oral infection helps prevent additional HSV-1 infections such as whitlow, genital herpes, and herpes of the eye. Prior HSV-1 seroconversion seems to reduce the symptoms of a later HSV-2 infection, although HSV-2 can still be contracted.
Many people infected with HSV-2 display no physical symptoms—individuals with no symptoms are described as asymptomatic or as having subclinical herpes. However, infection with herpes can be fatal.

Types of herpes

Condition	Description	Illustration
Herpetic gingivostomatitis	Herpetic gingivostomatitis is often the initial presentation during the first herpes infection. It is of greater severity than herpes labialis, which is often the subsequent presentation.
Herpes labialis	Commonly referred to as cold sores or fever blisters, herpes labialis is the most common presentation of recurrent HSV-1 infection following the re-emergence of the virus from the trigeminal nerve.
Herpes genitalis	When symptomatic, the typical manifestation of a primary HSV-1 or HSV-2 genital infection is clusters of inflamed papules and vesicles on the outer surface of the genitals resembling cold sores.
Herpetic whitlow and herpes gladiatorum	Herpes whitlow is a painful infection that typically affects the fingers or thumbs. On occasion, infection occurs on the toes or the nail cuticle. Individuals who participate in contact sports such as wrestling, rugby, and football, sometimes acquire a condition caused by HSV-1 known as herpes gladiatorum, scrumpox, wrestler's herpes, or mat herpes, which presents as skin ulceration on the face, ears, and neck. Symptoms include fever, headache, sore throat, and swollen glands. It occasionally affects the eyes or eyelids.
Herpesviral encephalitis and herpesviral meningitis	Herpes simplex encephalitis is a rare life-threatening condition that is thought to be caused by the transmission of HSV-1 either from the nasal cavity to the brain's temporal lobe or from a peripheral site on the face, along the trigeminal nerve axon, to the brainstem. Despite its low incidence, HSE is the most common sporadic fatal encephalitis worldwide. HSV-2 is the most common cause of Mollaret's meningitis, a type of recurrent viral meningitis.
Herpes esophagitis	Symptoms may include painful swallowing and difficulty swallowing. It is often associated with impaired immune function.

Other

is an HSV infection in an infant. It is a rare but serious condition, usually caused by vertical transmission of HSV-1 or -2 from mother to newborn. During immunodeficiency, herpes simplex can cause unusual lesions in the skin. One of the most striking is the appearance of clean linear erosions in skin creases, with the appearance of a knife cut. Herpetic sycosis is a recurrent or initial herpes simplex infection affecting primarily the hair follicles. Eczema herpeticum is an infection with herpesvirus in patients with chronic atopic dermatitis may result in spread of herpes simplex throughout the eczematous areas.
Herpetic keratoconjunctivitis, a primary infection, typically presents as swelling of the conjunctiva and eyelids, accompanied by small white itchy lesions on the surface of the cornea.
Herpetic sycosis is a recurrent or initial herpes simplex infection affecting primarily the hair follicle.

Bell's palsy

Although the exact cause of Bell's palsya type of facial paralysisis unknown, it may be related to the reactivation of HSV-1. This theory has been contested, however, since HSV is detected in large numbers of individuals having never experienced facial paralysis, and higher levels of antibodies for HSV are not found in HSV-infected individuals with Bell's palsy compared to those without. Antivirals may improve the condition slightly when used together with corticosteroids in those with severe disease.

Alzheimer's disease

HSV-1 has been proposed as a possible cause of Alzheimer's disease. In the presence of a certain gene variation, HSV-1 appears to be particularly damaging to the nervous system and increases one's risk of developing Alzheimer's disease. The virus interacts with the components and receptors of lipoproteins, which may lead to its development.

Pathophysiology

Herpes is contracted through direct contact with an active lesion or body fluid of an infected person. Herpes transmission occurs between discordant partners; a person with a history of infection can pass the virus to an HSV seronegative person. Herpes simplex virus 2 is typically contracted through direct skin-to-skin contact with an infected individual, but can also be contracted by exposure to infected saliva, semen, vaginal fluid, or the fluid from herpetic blisters. To infect a new individual, HSV travels through tiny breaks in the skin or mucous membranes in the mouth or genital areas. Even microscopic abrasions on mucous membranes are sufficient to allow viral entry.
HSV asymptomatic shedding occurs at some time in most individuals infected with herpes. It can occur more than a week before or after a symptomatic recurrence in 50% of cases. Virus enters into susceptible cells by entry receptors
such as nectin-1, HVEM and 3-O sulfated heparan sulfate. Infected people who show no visible symptoms may still shed and transmit viruses through their skin; asymptomatic shedding may represent the most common form of HSV-2 transmission. Asymptomatic shedding is more frequent within the first 12 months of acquiring HSV. Concurrent infection with HIV increases the frequency and duration of asymptomatic shedding. Some individuals may have much lower patterns of shedding, but evidence supporting this is not fully verified; no significant differences are seen in the frequency of asymptomatic shedding when comparing persons with one to 12 annual recurrences to those with no recurrences.
Antibodies that develop following an initial infection with a type of HSV can reduce the odds of reinfection with the same virus type. In a monogamous couple, a seronegative female runs a greater than 30% per year risk of contracting an HSV infection from a seropositive male partner. If an oral HSV-1 infection is contracted first, seroconversion will have occurred after 6 weeks to provide protective antibodies against a future genital HSV-1 infection. Herpes simplex is a double-stranded DNA virus.