Herpes Simplex Virus: Causes, Symptoms, Treatment

Herpes simplex virus (HSV) causes common infections of the skin, mouth, eyes, and genitals in humans. Once infected, the virus settles into the nerve roots and persists for life as a latent infection that occasionally causes symptoms. 8 11

There are two strains of the virus. HSV-1 is more common and usually infects the face, while HSV-2 is less common and usually infects the genitals. However, either strain can infect the face or genitals. 11

Infections are more common in women than men and often have no symptoms. There is currently no licensed vaccine or cure for HSV. 8 11 22

New research indicates a possible link between Alzheimer's disease and HSV infection.

How common is herpes?

As of 2016, 48% of Americans aged 14-49 had HSV-1 while 12% had HSV-2. Incidence of both strains have declined slightly since 1999. 22

Prevalence of both strains increases with age and differs across racial populations. HSV-1 is most common in Mexican-Americans, with at least 72% infected, while HSV-2 is most common in blacks, with at least 35% infected. 22

HSV-1 is slightly more common in women (51% of women vs 45% of men), but women have twice the rate of infection for HSV-2 (16% of women vs 8% of men). This difference is likely because genital infection is more easily transmitted from men to women during vaginal sex than from women to men. 11 22

Herpes types

Each strain of HSV has slightly different characteristics, however, they cause indistinguishable facial or genital lesions. 8

  • Herpes simplex virus type 1 (HSV-1) – This strain usually infects the trigeminal nerve root near the mouth. Oral HSV-1 is typically acquired in childhood which gives future protection to being infected genitally. However, because oral HSV-1 infections have declined in recent decades, people have become more susceptible to contracting the virus genitally and those infections are increasing. Having HSV-1 infection may mean that HSV-2 infection will not be as symptomatic or recur as frequently. 11 22 99 8
  • Herpes simplex virus type 2 (HSV-2) – This strain usually infects the sacral nerve root near the genitals and is acquired sexually. HSV-2 causes symptomatic genital recurrences at a much higher rate than HSV-1. This is possibly because HSV-1 is less likely to result in latent infection of the sacral nerve root and there may be biological differences in the ability to develop such an infection. 11 8 777

How is herpes spread?

HSV can be shed from normal-appearing skin and be in oral and genital fluids. In the United States, an estimated 87% of 14-49 year olds infected with HSV-2 have never received a clinical diagnosis. 11 22

Generally, a person can only get HSV-2 infection during genital contact with someone who has a genital HSV-2 infection. However, receiving oral sex from a person with an oral HSV-1 infection can result in getting a genital HSV-1 infection. 11

In people with symptomatic HSV-2 infections, shedding of the virus occurs on 20% of days, compared to 10% of days among those without symptoms. 11

A weakened immune system can make transmission and symptoms more likely. One interesting example is herpes virus reactivation in astronauts during space flights due to the environment that stresses their immune system. source

Symptoms of infection

People with symptoms may have painful blisters or sores at the site of infection, however, most individuals infected with HSV are asymptomatic or have very mild symptoms that go unnoticed or are mistaken for another skin condition. 11 22

People with suppressed immune function are at risk for systemic or disseminated infections that may require emergency care and antiviral therapy. source source

The average time between infection and symptoms for an initial herpes infection is 4 days after exposure. Symptoms of genital herpes differ between the first and subsequent outbreaks. 11

  • First outbreak – The first outbreak of herpes is often associated with a longer duration of blisters and sores, increased viral shedding (making HSV transmission more likely) and systemic symptoms including fever, body aches, swollen lymph nodes, or headache. 11
  • Recurrent outbreaks – Subsequent outbreaks of genital herpes are common, and many patients recognize early warnings such as genital pain, tingling, or shooting pains in the legs which occur hours to days before the symptoms appear. Recurrent outbreaks are typically shorter and less severe than the initial outbreak of genital herpes. Long-term studies have indicated that the number of symptomatic recurrent outbreaks may decrease over time. Also, recurrences and viral shedding are much less frequent for genital HSV-1 infection than for genital HSV-2 infection 11

Risks of having herpes

Having herpes may make it easier to spread HIV due to breaks in the skin and increase in cells that HIV target for entry. 11

Genital herpes can be passed to infant, potentially deadly – source

Herpes simplex encephalitis (HSE) – usually treated with Acyclovir, but resistant strains emerging source Infection of the brain

Alzheimer's disease and herpes

New research indicated a connection between Alzheimers and HSV infection. Herpes has been found in the brain of many people with Alzheimer's.

Detectible presence of HSV in the bloodstream increases with age. HSV can invade many brain regions. 4367

In the nervous system, HSV1 can latently persist for decades, notably in the trigeminal ganglia, but can invade many brain regions. HSV1 receptors are most abundantly expressed in the hippocampus, a site of early degeneration in AD. 4367

There are also suggestions that a declining immune system in the elderly might predispose to virus reactivation: the immune system undergoes systemic changes over a lifetime and reactivation of HSV1 has been reported to take place as a function of age. 4367

  • parkinsons, alzheimer's. HSV could initiate an autoimmune reaction against the host’s nerve cells. The nerve cells have proteins that resemble portions of the virus from a structural and genetic stand point. 951
  • In a large population-based cohort study there is an association between HSV carriage and declining episodic memory function, especially among APOE ɛ4 carriers. The results strengthen the hypothesis that HSV is associated with Alz development. 627

Herpes treatment

  • Acyclovir antiviral – Acyclovir can alleviate the symptoms of herpes infection and speed the healing process. In addition, it can reduce recurrences when used for suppressive therapy. However, it does not decrease the frequency of subsequent recurrences. 8
  • Foscarnet – x
  • Mesenchemal stem cells – These fndings indicate that MSC therapy is a prospective approach to the development of new effective management of generalized HSV1 infection. source
  • Frog skin – this study extends the little studied anti-viral attributes of frog temporins and offers perspectives for the development of new anti-HSV-1 therapies. source

Common questions

  • If I have oral HSV1 can I get genital HSV1? – Very unlikely. This is a good question because most people already have an HSV1 infection. Leading idea is that we build up resistance which makes it unlikely, but we don't have statistics so we're not 100% sure. source source source 777
  • A case study of a concurrent oral/genital infection has been reported. source
  • How soon after risky sex would an outbreak occur? – x
  • Does having one strain of herpes protect against the other? – Having HSV1 previously may mean HSV2 infection may not be as symptomatic or recur as frequently. 99

Transmission commonly occurs from contact with an infected person who does not have visible symptoms and may not even know they're infected.  11

Once reactivated, HSV travels along the nerves back to the skin to form new blisters where shedding of the virus occurs. However,

Importantly, already having a herpes type 1 infection makes it extremely unlikely you'll get a genital herpes type 1 infections. So being exposed to herpes isn't necessarily a bad thing.

Having herpes type 1 does not seem to protect against HSV2 infections. But having HSV2 actually does seem to protected against HSV1.

  • Herpes type 1 – Usually infects orally without sex or kissing at a young age. If infected orally you're at a lower chance of getting an HSV1 infection genitally. Antivirals to avoid spreading to partner.

How to prevent infection

The viruses are transmitted through contact with an infected person’s lesion, mucosal surface, or genital or oral secretions. 22


  • Antivirals – Antivirals to avoid spreading to partner.
  • Acyclovir can alleviate the symptoms of herpes infection and speed the healing process. 8

Type 2 – doesn't like to infect orally. So receiving oral sex from someone with an unknown herpes status is low risk