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.
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 about 8–11%. This is believed to be due to the increased exposure of mucosal tissue to potential infection sites. Transmission risk from infected female to male is around 4–5% annually. Suppressive antiviral therapy reduces these risks by 50%. Antivirals also help prevent the development of symptomatic HSV in infection scenarios, meaning the infected partner will be seropositive but symptom-free by about 50%. Condom use also reduces the transmission risk significantly. Condom use is much more effective at preventing male-to-female transmission than vice versa. Previous HSV-1 infection may reduce the risk for acquisition of HSV-2 infection among women by a factor of three, although the one study that states this has a small sample size of 14 transmissions out of 214 couples.
These herpes viruses enter the body through small cuts, abrasions, or breaks in the skin or mucous membranes. The incubation period for herpes simplex infections is about three to six days. Transmission (spread) of the virus is person to person and more likely to occur if blisters or lesions are present. The majority enter after an uninfected person has direct contact with someone carrying the virus (either with or without noticeable lesions). Simply touching an infected person is often the way children get exposed. Adolescents and adults frequently get exposed by skin contact but may get their first exposure by kissing or sexual contact (oral and/or genital contact), especially for HSV-2. Statistical studies suggest that about 80%-90% of people in the U.S. have been exposed to HSV-1 and about 30% have been exposed to HSV-2. Usually, the contagious period continues until lesions heal. Some people (estimated from 30%-50%) occasionally shed herpes virus while having few or no associated symptoms or signs.
Herpes has been known for at least 2,000 years. Emperor Tiberius is said to have banned kissing in Rome for a time due to so many people having cold sores. In the 16th-century Romeo and Juliet, blisters "o'er ladies' lips" are mentioned. In the 18th century, it was so common among prostitutes that it was called "a vocational disease of women". The term 'herpes simplex' appeared in Richard Boulton's A System of Rational and Practical Chirurgery in 1713, where the terms 'herpes miliaris' and 'herpes exedens' also appeared. Herpes was not found to be a virus until the 1940s.
The most effective method of avoiding genital infections is by avoiding vaginal, oral, 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 (acetaminophen) 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.
Herpes antiviral therapy began in the early 1960s with the experimental use of medications that interfered with viral replication called deoxyribonucleic acid (DNA) inhibitors. The original use was against normally fatal or debilitating illnesses such as adult encephalitis, keratitis, in immunocompromised (transplant) patients, or disseminated herpes zoster. The original compounds used were 5-iodo-2'-deoxyuridine, AKA idoxuridine, IUdR, or(IDU) and 1-β-D-arabinofuranosylcytosine or ara-C, later marketed under the name cytosar or cytarabine. The usage expanded to include topical treatment of herpes simplex, zoster, and varicella. Some trials combined different antivirals with differing results. The introduction of 9-β-D-arabinofuranosyladenine, (ara-A or vidarabine), considerably less toxic than ara-C, in the mid-1970s, heralded the way for the beginning of regular neonatal antiviral treatment. Vidarabine was the first systemically administered antiviral medication with activity against HSV for which therapeutic efficacy outweighed toxicity for the management of life-threatening HSV disease. Intravenous vidarabine was licensed for use by the U.S. Food and Drug Administration in 1977. Other experimental antivirals of that period included: heparin, trifluorothymidine (TFT), Ribivarin, interferon, Virazole, and 5-methoxymethyl-2'-deoxyuridine (MMUdR). The introduction of 9-(2-hydroxyethoxymethyl)guanine, AKA aciclovir, in the late 1970s raised antiviral treatment another notch and led to vidarabine vs. aciclovir trials in the late 1980s. The lower toxicity and ease of administration over vidarabine has led to aciclovir becoming the drug of choice for herpes treatment after it was licensed by the FDA in 1998. Another advantage in the treatment of neonatal herpes included greater reductions in mortality and morbidity with increased dosages, which did not occur when compared with increased dosages of vidarabine. However, aciclovir seems to inhibit antibody response, and newborns on aciclovir antiviral treatment experienced a slower rise in antibody titer than those on vidarabine.
Although the exact cause of Bell's palsy—a type of facial paralysis—is unknown, it may be related to 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.
Herpes infection can be passed from you to your unborn child before birth but is more commonly passed to your infant during delivery. This can lead to a potentially deadly infection in your baby (called neonatal herpes). It is important that you avoid getting herpes during pregnancy. If you are pregnant and have genital herpes, you may be offered anti-herpes medicine towards the end of your pregnancy. This medicine may reduce your risk of having signs or symptoms of genital herpes at the time of delivery. At the time of delivery, your doctor should carefully examine you for herpes sores. If you have herpes symptoms at delivery, a ‘C-section’ is usually performed.
A doctor will base a presumptive diagnosis on information provided by the patient and on the physical examination. The characteristic appearance of the herpes sores leaves little doubt about the diagnosis, so the typical appearance of the sores is key to the diagnosis. This appearance helps distinguish oral herpes from oral thrush, shingles, gonorrhea, and syphilis. In addition, chapped or sunburned lips can resemble oral herpes, but the tissue stain (Tzanck smear, see below) shows no virus-induced cell changes. Further testing is usually not necessary but is sometimes done.