Glossary of Medical and Health Terms

Herpes Simplex (Anogenital Herpesviral)

Herpes simplex is a viral disease caused by herpes simplex viruses that primarily infect mucosal tissues and skin. Infection of the genitals is commonly known as herpes and is predominantly caused by the type 2 strain of herpes simplex virus (HSV-2), which is usually sexually transmitted. Oral herpes, colloquially called cold sores, and sometimes mistaken for canker sores, is usually caused by the type 1 strain of herpes simplex virus (HSV-1). These viruses infect the skin to cause conditions called herpes whitlow and herpes gladiatorum, and can infect the eye to cause ocular herpes. More serious disorders are caused by these viruses when they infect the central nervous system - these include herpes encephalitis, Mollaret's meningitis, and possibly Bell's palsy. In newborn babies, infection by herpes viruses (neonatal herpes) can be very serious, resulting in brain damage or even death of the infant. Neonatal HSV is more likely in a mother that acquired a primary HSV infection shortly before giving birth, such that she lacks protective antibodies that would otherwise reduce viable virus shedding.

Although HSV-1 is classically associated with oral herpes, an increasing number of genital herpes infections are caused by this virus. HSV-1 genital herpes is more infectious during primary episodes than HSV-2, but reoccurs less frequently. Both viruses cause periods of active disease lasting 2-21 days, followed by remission when the sores disappear. Most cases of genital herpes are asymptomatic, although shedding may still occur. Over time, periods of remission generally increase in length, and the duration of lesions and viral shedding decrease, leading to reduced episodes of active disease. The frequency of recurrences is regulated by specific immunity developed against the virus. Previous HSV-1 infection tends to ameliorate the symptoms of a subsequent HSV-2 infection.

HSV-1 and HSV-2 are transmitted by direct contact with a sore or body fluid of an infected individual, and can cause painful fluid-filled blisters, containing millions of infectious virus particles. After initial infection, these viruses travel from cells in the skin to sensory nerves, where they reside as life-long, latent viruses. HSV-1 lies dormant in trigeminal ganglia that provide sensation to the lips, lower mouth and neck; HSV-2 resides in sacral ganglia that supply sensation to the genitals, perineum and upper legs. Occasionally, these viruses reactivate. When this occurs, HSV travels down the same nerves to reinfect the same area of skin infected during the primary infection. Recurrences can be triggered in some individuals by specific events, such as sunburn, ultraviolet light, wind, trauma, surgery, stress or other infections. Since viral reactivation is controlled by the immune system, in immunocompetent persons, oral and genital herpes are not typically life-threatening. Individuals with HIV and transplant patients have compromised immune systems, and can develop serious HSV infections such as keratitis or encephalitis. Similarly, immuno-incompetent newborns, infected by genital herpes at birth or shortly thereafter, are at highest risk if they acquire central nervous system HSV infection that can cause brain damage or disseminated HSV which often results in liver failure and death.

Prevalence of HSV-1 and HSV-2 infections varies throughout the world. Socioeconomic status appears to be an important factor associated with HSV-1 infection levels with developing countries, such as those in Sub-Saharan Africa, showing higher levels of HSV-1 and younger acquisition rates than industrialized countries like the United States and countries in Northern Europe. The risk of infection for HSV-1 is associated with lower income and a more crowded living environment. HSV-2 seroprevalence is also highest in Sub-Saharan Africa, affecting more than 80% of the population in some countries. Levels of HSV-2 infections are much lower in the U.S., affecting approximately 20-30% of the adult population, but this is still high compared to other industrialized countries such as Australia (12%), the United Kingdom (4%) and Germany (14%). Females appear to be more at risk than males, for acquiring HSV-2, and the chance of being infected increases with age, and with commencing sexual activity at a younger age.

Various treatments are available to reduce the symptoms and speed up the healing process of herpes outbreaks but there is currently no cure for herpes. Antiviral mediations, such as aciclovir and valaciclovir, taken orally, reduce viral reproduction and shedding, and some topical creams, such as Docosanol and Tromantadine prevent the virus from entering the skin. Some other drugs reduce herpetic symptoms by synergising with oral antiviral medication; Cimetidine and probenecid can reduce aciclovir clearance and aspirin can reduce inflammation associated with viral infection. Some natural remedies may have potential benefits in reducing herpes outbreaks and/or their symptoms. No vaccine is currently available to prevent or treat herpes. However, trials are currently underway to identify a suitable vaccine against HSV-2.

Associated ICD-10 code: A60, B00, G05.1, P35.2.

Source: http://en.wikipedia.org/wiki/Herpes_simplex

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