Herpes

Herpes refers to the diseases caused by Herpes Simplex Virus (HSV), an important cause of human disease. In people symptomatic herpes siplex infections take two common forms, a recurrent rash of swollen blisters in the area of the mouth, and a similar rash in the area of the genitals. The two subtypes are responsible for cold sores and genital herpes, a recurrent, painful genital rash. Genital herpes is considered a sexually transmitted disease (STD).

The virus

Herpes Simplex Virus (HSV) is a member of the Herpesviridae family of viruses, a family of DNA viruses important in human disease. These include Human herpesviruses (HHV)1-8 (see Herpes Viruses). HSV 1 and 2 correspond to HHV 1 and 2. HSV 1 and 2 are very prevalent in the human population, with as many as 30-70% of people testing positive for antibodies in their lifetime.

Natural history of human infection

HSV 1 and 2 are DNA viruses that cause common human illnesses, and infection is life-long. In general, HSV 1 is more commonly seen on the face, and HSV 2 is more commonly seen on the genitalia. The virus is spread by simple person-to-person contact and can occur when sores are visible, and when the virus is dormant, although this is less effective. These viruses generally cause mucocutaneous infection. This can manifest as cold sores on the lips, or as genital sores. The typical rash is described as "dew drops on a rose pedal". These are generally painful. Initial infection can be accompanied by systemic systems such as fever and muscle aches. After resolution of the initial infection, the virus becomes dormant in the human host. Under certain conditions that are not well understood, the virus is reactivated, with a recurrence of mucocutaneous infection. These recurrent attacks are unpredictable and can be frequent or infrequent. In addition to the common mucocutaneous infection, HSV 1 and 2 can also cause keratitis (inflammation in the eye), encephalitis (brain infection), and severe neonatal disease if acquired during pregnancy.

Diagnosis

the diagnosis of a herpes simplex infection is ordinarily a clinical one, that is based on the history and physical findings. However, a clinical diagnosis does not distinguish between HSV-1 and HSV-2 infection, except by probability. Confirming a diagnosis and clarifying the actual virus type involve requires culturing the virus from the patient. Although primary ulcers have a high rate of viral shed, recurrent lesions shed virus at a much lower rate, and so culture of recurrent lesions has a high false negative rate. Accordingly, in patients with typical presentations of recurrent outbreaks known to be caused by the Herpes Simplex virus, failure to culture the virus in no way overturns the diagnosis.

Genital herpes infection

In population studies in the United States, both serotypes of the herpes virus are prevalent in symptomatic genital herpes infections. HSV-2 accounting for more than half, and HSV-1 for almost half of infections. More than 50 million people are infected in that country, making this the most common STD in the USA.

Although both types of herpes simplex virus can account for genital herpes, and cause a very similar appearing rash, "HSV-1 has a much lower recurrence rate. For example, 40% of patients with an initial episode of HSV-1 will remain asymptomatic during the first year of infection, while 40% of patients with an initial outbreak of HSV-2 will have six or more recurrences per year." (reference for quote:Kirkland LG. New developments in the management of STDs. [Review] [10 refs] [Journal Article. Review] Nurse Practitioner. 31(12):12-21; quiz 22-3, 2006 Dec. UI: 17149130 )

The Center for Disease Control (CDC) in the United States recommends that genital lesions be cultured in order to determine the type of HSV infection.

Prevention and Treatment

Because HSV 2 is spread more commonly by sexual contact, it is easier to prevent than HSV 1. There is currently no vaccine available for either virus. Avoiding contact with people who have obvious sores helps reduce infection, and prophylaxis with commonly available antiviral drugs can help prevent transmission during the latent phase of the illness. Prophylaxis can also be given to reduce frequency and severity of attacks. Consistent and correct use of condoms reduces transmission.

References

Goldman: Cecil Textbook of Medicine, 22nd ed., Copyright © 2004 W. B. Saunders Company

Cohen & Powderly: Infectious Diseases, 2nd ed., Copyright © 2004 Mosby, An Imprint of Elsevier