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Herpes simplex virus 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 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. Newborns exposed to the virus during passage through the birth canal can develop a severe multi-organ infection. Infection of immunocompromised patients such as HIV-infected persons, bone marrow or organ transplant recipients, can be very serious including severe life-threatening pneumonia. HSV can also reactivate from latency in the immunocompromised and cause severe generalized infections.


Both viruses are transmitted by intimate contact with oral and genital secretions such as occurs between mother and child or siblings. HSV can also be transmitted during sexual contact.


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


A person who has been infected HSV will develop antibodies to the virus that will stay in the body for the rest of that person’s life. A blood test for these antibodies can tell whether a person has been infected sometime in the past with HSV. To detect an active infection a test that detects the virus in either by viral culture or polymerase chain reaction (PCR) must be performed.


There's no cure for HSV, and treatment for the virus generally is not recommended for healthy patients. Patients with frequent recurrent reactivation of genital herpes can benefit from regular suppressive treatment with antivirals such as valaciclovir which can reduce the frequency and severity of outbreaks.  Suppressive therapy also reduces transmission to sexual partners. Patients with encephalitis, newborns, and people with compromised immune systems do need treatment for HSV infection. Antiviral drugs such as acyclovir and are available that slow down the virus reproduction and reduce symptoms, but cannot eliminate the virus.

Recommended Reading


Whitley, R.J., Herpes Simplex Virus Infections, Goldman: Cecil Textbook of Medicine, 21st Edition, ©2000 W. B. Saunders Company.


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