Herpes simplex a viral disease caused by herpes simplex viruses; both herpes simplex virus 1 (HSV-1) and herpes simplex virus 2 (HSV-2) cause herpes simplex. Infection with the herpes virus is categorized into one of several distinct disorders based on the site of infection. Oral herpes, the visible symptoms of which are colloquially called cold sores, infects the face and mouth. Oral herpes is the most common form of infection. Genital herpes, commonly known simply as herpes, is the second most common form of herpes. Other disorders such as herpetic whitlow, herpes gladiatorum, ocular herpes (keratitis), cerebral herpes infection encephalitis, Mollaret’s meningitis, neonatal herpes, and possibly Bell’s palsy are all caused by herpes simplex viruses.
Signs and Symptoms
HSV infection causes several distinct medical disorders. Common infection of the skin or mucosa may affect the face and mouth (orofacial herpes), genitalia (genital herpes), or hands (herpes whitlow). More serious disorders occur when the virus infects and damages the eye (herpes keratitis), or invades the central nervous system, damaging the brain (herpes encephalitis). Patients with immature or suppressed immune systems, such as newborns, transplant recipients, or AIDS patients 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.
Diagnosis of Herpes simplex
Primary orofacial herpes is readily identified by clinical examination of persons with no previous history of lesions and contact with an individual with known HSV-1 infection. The appearance and distribution of sores in these individuals typically presents as multiple, round, superficial oral ulcers, accompanied by acute gingivitis. Adults with non-typical presentation are more difficult to diagnose. Prodromal symptoms that occur before the appearance of herpetic lesions help differentiate HSV symptoms from the similar symptoms of other disorders, such as allergic stomatitis. When lesions do not appear inside the mouth primary orofacial herpes is sometimes mistaken for impetigo, a bacterial infection. Common mouth ulcers (aphthous ulcer) also resemble intraoral herpes, but do not present a vesicular stage.
Genital herpes can be more difficult to diagnose than oral herpes since most HSV-2-infected persons have no classical symptoms. Further confusing diagnosis, several other conditions resemble genital herpes, including lichen planus, atopic dermatitis, and urethritis. Laboratory testing is often used to confirm a diagnosis of genital herpes. Laboratory tests include: culture of the virus, direct fluorescent antibody (DFA) studies to detect virus, skin biopsy, and polymerase chain reaction (PCR) to test for presence of viral DNA. Although these procedures produce highly sensitive and specific diagnoses, their high costs and time constraints discourage their regular use in clinical practice.
Serological tests for antibodies to HSV are rarely useful to diagnosis and not routinely used in clinical practice, but are important in epidemiological studies. Serologic assays cannot differentiate between antibodies generated in response to a genital versus or an oral HSV infection, and as such cannot confirm the site of infection. Absence of antibody to HSV-2 does not exclude genital infection because of the increasing incidence of genital infections caused by HSV-1.
Prevention of Herpes simplex
Barrier protection, such as a condom, can reduce the risk of herpes transmission.
For genital herpes, condoms are highly effective in limiting transmission of herpes simplex infection. The virus cannot pass through latex, but a condom’s effectiveness is somewhat limited on a public health scale by their limited use in the community, and on an individual scale because the condom may not completely cover blisters on the penis of an infected male, or the base of the penis or testicles not covered by the condom may come into contact with free virus in vaginal fluid of an infected female. In such cases, abstinence from sexual activity or washing of the genitals after sex is recommended. The use of condoms or dental dams also limits the transmission of herpes from the genitals of one partner to the mouth of the other (or vice versa) during oral sex.
As with almost all sexually transmitted infections, women are more susceptible to acquiring genital HSV-2 than men. On an annual basis, without the use of antivirals or condoms, the transmission risk of HSV-2 from infected male to female is approximately 8-10%.
The risk of transmission from mother to baby is highest if the mother becomes infected at around the time of delivery (transmission risk 30 to 60%), but the risk falls to 3% if it is a recurrent infection, and is less than 1% if there are no visible lesions. To prevent neonatal infections, seronegative women are recommended to avoid unprotected oral-genital contact with an HSV-1 seropositive partner and conventional sex with a partner having a genital infection during the last trimester of pregnancy.
HSV-2 infected individuals are at higher risk for acquiring HIV when practicing unprotected sex with HIV positive persons, particularly during an outbreak with active lesions.
Treatment of Herpes simplex
Antiviral medications used against herpes viruses work by interfering with viral replication, effectively slowing the replication rate of the virus and providing a greater opportunity for the immune response to intervene. All drugs in this class depend on the activity of the viral enzyme thymidine kinase to convert the drug sequentially from its prodrug form to monophosphate (with one phosphate group), diphosphate (with two phosphate groups), and finally to the triphosphate (with three phosphate groups) form which interferes with viral DNA replication.
There are several prescription antiviral medications for controlling herpes simplex outbreaks, including aciclovir (Zovirax), valaciclovir (Valtrex), famciclovir (Famvir), and penciclovir. Aciclovir was the original, and prototypical, member of this drug class; it is now available in generic brands at a greatly reduced cost. Valaciclovir and famciclovir—prodrugs of aciclovir and penciclovir, respectively—have improved solubility in water and better bioavailability when taken orally. Aciclovir is the recommended antiviral for suppressive therapy for use during the last months of pregnancy to prevent transmission of herpes simplex to the neonate in cases of maternal recurrent herpes. The use of valaciclovir and famciclovir, while potentially improving treatment compliance and efficacy, are still undergoing safety evaluation in this context.
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