Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), also known by their taxonomical names Human alphaherpesvirus 1 and Human alphaherpesvirus 2, are two members of the human Herpesviridae family, a set of viruses that produce viral infections in the majority of humans. Both HSV-1 (which produces most cold sores) and HSV-2 (which produces most genital herpes) are common and contagious. They can be spread when an infected person begins shedding the virus.
About 67% of the world population under the age of 50 has HSV-1. In the United States, about 47.8% and 11.9% are believed to have HSV-1 and HSV-2, respectively. Because it can be transmitted through any intimate contact, it is one of the most common sexually transmitted infections.
Many of those who are infected never develop symptoms.when they occur, may include watery blisters in the skin or mucous membranes of the mouth, lips, nose, or genitals. Lesions heal with a scab characteristic of herpetic disease. Sometimes, the viruses cause mild or atypical symptoms during outbreaks. However, they can also cause more troublesome forms of herpes simplex. As neurotropic and neuroinvasive viruses, HSV-1 and -2 persist in the body by hiding from the immune system in the cell bodies of neurons. After the initial or primary infection, some infected people experience sporadic episodes of viral reactivation or outbreaks. In an outbreak, the virus in a nerve cell becomes active and is transported via the neuron's axon to the skin, where virus replication and shedding occur and cause new sores.
The herpes viruses establish lifelong infections (thus cannot be eradicated from the body).Because the virus is a foreign pathogen, a human body's immune system as well as its specialty antigen naturally diminishes the virus.
Treatment usually involves general-purpose antiviral drugs that interfere with viral replication, reduce the physical severity of outbreak-associated lesions, and lower the chance of transmission to others. Studies of vulnerable patient populations have indicated that daily use of antivirals such as acyclovir and valaciclovir can reduce reactivation rates.
HSV-1 and HSV-2 are transmitted by contact with an infected person who has reactivations of the virus. HSV-2 is periodically shed in the human genital tract, most often asymptomatically. Most sexual transmissions occur during periods of asymptomatic shedding. Asymptomatic reactivation means that the virus causes atypical, subtle, or hard-to-notice symptoms that are not identified as an active herpes infection, so acquiring the virus is possible even if no active HSV blisters or sores are
present. In one study, daily genital swab samples found HSV-2 at a median of 12–28% of days among those who have had an outbreak, and 10% of days among those suffering from asymptomatic infection, with many of these episodes occurring without visible outbreak ("subclinical shedding").
In another study, 73 subjects were randomized to receive valaciclovir 1 g daily or placebo for 60 days each in a two-way crossover design. A daily swab of the genital area was self-collected for HSV-2 detection by polymerase chain reaction, to compare the effect of valaciclovir versus placebo on asymptomatic viral shedding in immunocompetent, HSV-2 seropositive subjects without a history of symptomatic genital herpes infection. The study found that valaciclovir significantly reduced shedding during subclinical days compared to placebo, showing a 71% reduction; 84% of subjects had no shedding while receiving valaciclovir versus 54% of subjects on placebo. About 88% of patients treated with valaciclovir had no recognized signs or symptoms versus 77% for placebo.
For HSV-2, subclinical shedding may account for most of the transmission. Studies on discordant partners (one infected with HSV-2, one not) show that the transmission rate is approximately 5 per 10,000 sexual contacts. Atypical symptoms are often attributed to other causes, such as a yeast infection. HSV-1 is often acquired orally during childhood. It may also be sexually transmitted, including contact with saliva, such as kissing and mouth-to-genital contact (oral sex). HSV-2 is primarily a sexually transmitted infection, but rates of HSV-1 genital infections are increasing.
Both viruses may also be transmitted vertically during childbirth. However, the risk of infection transmission is minimal if the mother has no symptoms or exposed blisters during delivery. The risk is considerable when the mother is infected with the virus for the first time during late pregnancy.Contrary to popular myths, herpes cannot be transmitted from surfaces such as toilet seats because the herpes virus begins to die immediately after leaving the body.
Herpes simplex viruses can affect areas of skin exposed to contact with an infected person (although shaking hands with an infected person does not transmit this disease). An example of this is herpetic whitlow, which is a herpes infection on the fingers. This was a common affliction of dental surgeons prior to the routine use of gloves when conducting treatment on patients.
Infection of HSV-2 increases the risk of acquiring HIV.
Journal of Infectious Diseases & Therapy
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