Cold Sores

Herpes simplex virus 1 and 2 (HSV-1 and HSV-2), also known as Human herpes virus 1 and 2 (HHV-1 and -2), are two members of the herpes virus family, Herpesviridae, that infect humans. Both HSV-1 and -2 are ubiquitous and contagious. They can be spread when an infected person is producing and shedding the virus.

Symptoms of herpes simplex virus infection include watery blisters in the skin or mucous membranes of the mouth, lips or genitals. Lesions heal with a scab characteristic of herpetic disease. However, as neurotropic and neuroinvasive viruses, HSV-1 and -2 persist in the body for the life of the carrier by becoming latent and hiding from the immune system in the cell bodies of nerves. 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 transportated via the nerve's axon to the skin, where virus replication and shedding occur and cause new sores.

There is no known cure for HSV infection, but treatments can reduce the likelihood of viral shedding and spread.

Transmission

HSV-1 and -2 are transmitted horizontally during close contact with an infected person who is shedding virus from the skin, often in saliva or in secretions from the genitals. Transmission is more likely to occur when sores are present, although viral shedding and transmission can occur in the absence of visible sores and most HSV-2 infections result from asymptomatic shedding. HSV-1 is usually acquired orally during childhood, but may also be sexually transmitted. HSV-2 is primarily a sexually transmitted infection.

Both viruses may also be transmitted vertically from mother to child before or during childbirth. The risk of infection is reduced if the mother has no symptoms or exposed blisters during delivery. Some forms of HSV can be fatal to the infant, as the developing immune system of the child is unable to defend against the virus, resulting in inflammation of the brain (encephalitis) that may cause brain damage.

Symptoms resulting from primary infection with HSV are usually more severe than subsequent outbreaks, as the body has not had a chance to produce antibodies. This first outbreak carries a low (≈1%) risk of developing aseptic meningitis.

Treatment and vaccine development

Herpes viruses establish lifelong infections and the virus cannot currently be eradicated from the body. Treatment usually involves general-purpose antiviral drugs that interfere with viral replication, reducing the physical severity of outbreak-associated lesions and lowering the chance of transmission to others. Studies of vulnerable patient populations have indicated that daily use of antivirals such as acyclovir and valacyclovir can reduce HSV-2 shedding by 60-80% and cut HSV-2 transmission risk in half.

In vitro research has indicated that Aloe Vera may be effective against genital herpes.

Research into a vaccine is ongoing. Efforts to develop an effective vaccine have so far been hampered by the many adaptations of HSVs to their human hosts during an evolutionarily ancient relationship.