STI | Herpes simplex virus

Herpes simplex virus (HSV) is transmitted by intimate contact with oral and genital secretions during sexual contact and typically causes sores with clear-appearing fluid of the mouth, genitalia or skin.  

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Herpes simplex virus (HSV) types 1 and 2 are members of the Herpesviridae family of viruses which are large DNA viruses. HSV-1 and HSV-2 are also referred to as human herpesvirus types 1 and 2 (HHV-1 and HHV-2) and belong to the Alphaherpesvirinae subfamily that includes human herpesvirus type 3 (HHV-3) also known as varicella-zoster virus.


HSV-1 and HSV-2 (collectively HSV) are similar viruses but are distinct antigenically and biologically. Whereas both viruses infect mucocutaneous tissue, HSV-1 tends to cause infections of the oral mucosa (cold sores) and HSV-2 causes infections of the genital tract (genital herpes). However, there is an overlap. The typical lesions caused by these viruses are vesicles (sores with clear-appearing fluid) of the mouth, genitalia or skin. Both viruses are transmitted by intimate contact with oral and genital secretions including sexual contact. Like all herpesviruses, HSV-1 and HSV-2 can become latent in an infected person and remain present in the body throughout the remainder of life. HSV-1 and HSV-2 establish latency in the neurons that innervate infected tissue. For HSV-1 this involves the cranial nerves, particularly the trigeminal ganglia. For HSV-2 this involves the sacral nerves. The virus remains in a dormant state during latency but can reactivate following periods of stress and cause lesions near the site of the original infection.


HSV can cause severe infections of the nervous system including meningitis and encephalitis. Infection of immunocompromised patients, such as HIV-infected persons and bone marrow or organ transplant recipients, can be very serious, including severe and life-threatening pneumonia. HSV can also reactivate from latency in the immunocompromised and cause severe generalized infections.

Both HSV-1 and HSV-2 are transmitted via close or intimate contact with oral and/or genital secretions. HSV can also be transmitted during sexual contact.

HSV-2 is most commonly the cause of genital infections, due to venereal transmission, while HSV-1 is commonly associated with other disease locations although both serotypes have been shown to cause disease in all locations of the body. 

Newborns exposed to the virus during passage through the birth canal can develop a severe multi-organ infection. Studies have shown an increasing prevalence of genital HSV infections with a concomitant increase of the disease in neonates.

There is not a vaccine for HSV. The most effective means of preventing transmission of HSV is for infected individuals to avoid close contact with others when they have active lesions.

Measures that may help prevent the spread of herpes include:

  • Avoiding sexual activity during an outbreak
  • Using condoms or a dental dam during oral, genital or anal sexual contact 
  • Showering or bathing with soap and water after sex

Suppressive therapy by taking antiviral drugs may decrease the risk of transmission.


To diagnose a herpes infection, a sample of an active sore can be tested. A blood test for herpes antibodies can tell whether an individual has been infected sometime in the past with HSV. To detect an active infection, a test that detects the virus either by viral culture or polymerase chain reaction (PCR) will be performed.

There’s no cure for HSV, and treatment for the virus generally is not recommended for healthy individuals. Newborns, as well as patients with encephalitis, compromised immune systems and frequent recurrent reactivation of genital herpes can benefit from regular suppressive treatment to reduce the frequency and severity of outbreaks by using daily antivirals such as:  

  • Acyclovir
  • Famciclovir 
  • Valacyclovir

Antiviral drugs slow down the virus reproduction and reduce symptoms of HSV but cannot eliminate the virus. 


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