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Herpes

Also known as: Herpes culture; Herpes simplex viral culture; HSV DNA; HSV by PCR; HSV-1 or HSV-2 IgM or IgG; HSV-1; HSV-2; HHV1; HHV2
Formal name: Herpes Simplex Virus, Type1 and Type 2
Related tests: TORCH; CSF analysis

At a Glance

Why Get Tested?

To screen for or diagnose infection with the herpes simplex virus

When to Get Tested?

If you have symptoms of an infection with the herpes simplex virus, such as blisters in the genital area or symptoms of viral meningitis

Sample Required?

A swab or scraping from a blister or sore in the infected area or a blood sample drawn from a vein in your arm; for meningitis or encephalitis, a sample of cerebrospinal fluid

Test Preparation Needed?

None

The Test Sample

What is being tested?

Herpes simplex testing is performed to identify an acute herpes infection or to detect herpes antibodies, an indication of a previous exposure to herpes. One of the most common viral infections, herpes simplex virus (HSV) exists as two main types, HSV-1 and HSV-2. Both types are contagious and periodically cause small fever blisters (vesicles) that break to form open lesions. HSV-1 primarily causes blisters or "cold sores" around the oral cavity and mouth, while HSV-2 usually causes lesions around the genital area; however, either one can affect the oral or genital area.

The herpes simplex virus can be passed from person to person through skin contact while the sores are open and healing and sometimes asymptomatically when there are no visible sores. HSV-2 is frequently a sexually transmitted disease, but HSV-1 also may be acquired during oral sex and found in the genital area. According to the American Social Health Association and their National Herpes Resource Center, about 50% to 80% of adults in the U.S. have HSV-1 and about 20% have HSV-2. Because symptoms may be mild, 90% of those who have HSV-2 may be unaware that they have been infected.

When someone is first infected, he or she may have obvious and painful blisters at the site of infection, which usually appear within two weeks after the virus is transmitted and usually heal within two to four weeks. The blisters can appear in the vaginal area, on the penis, around the anus, or on the buttocks or thighs. This primary episode can include a second outbreak of blisters and even flu-like symptoms of fever and swollen glands. However, not everyone develops blisters and sometimes symptoms are so mild that they are unnoticeable or mistaken for something else, such as insect bites or a rash.

Once someone is infected and the initial infection resolves, he or she will harbor the HSV in a latent form. During periods of stress or illness, the virus may reactivate. In most cases, HSV outbreaks are a painful annoyance rather than a health threat, but the virus can also cause neonatal herpes (an infant may be infected by a mother who has active genital herpes during birth) and encephalitis. These illnesses can be fatal and can cause serious permanent neurological problems in those who survive. Patients with conditions that cause their immune system to be suppressed, such as those with HIV/AIDS or those who have had an organ transplant, may have more frequent and serious outbreaks of HSV. While there is no cure for herpes, antiviral medications are available that suppress outbreaks and shorten the duration of active shedding of virus and of symptoms.

HSV testing detects either the virus itself, its viral DNA, or antibodies to the virus. During an acute primary infection or reactivation, the virus may be detected by:

  • Herpes culture. A sample of fluid is collected from an open sore (the most common sample). It is incubated in a nutrient environment to grow and isolate the virus. This test is sensitive and specific, but it takes 2 or more days to complete. Fresh lesions are the best for this test. Viral shedding decreases over time and can lead to a false negative result. Once the virus is grown in culture, it is possible to determine if it is HSV-1 or HSV-2.
  • HSV DNA testing. Can be done to detect HSV genetic material in a patient sample. DNA testing is usually done only if the culture is negative but the physician still suspects herpes or if the patient is being treated for herpes. This method can detect the virus as well as identify the type and is good in circumstances where the virus is present in low numbers (such as viral encephalitis) or if the lesion is several days old. This is the best method to detect HSV meningitis, encephalitis, or keratitis because this method is more sensitive.
  • HSV antibody testing. Antibodies to HSV are specific proteins that the body creates and releases into the bloodstream to fight the infection. HSV IgM antibody production begins several days after a primary (initial) HSV infection and may be detectable in the blood for several weeks. HSV IgG antibody production begins after HSV IgM production. Concentrations rise for several weeks, fall, and then stabilize in the blood. Once someone has been infected with HSV, they will continue to produce small quantities of HSV IgG. HSV antibody testing can detect both viral types (HSV-1 and HSV-2), and tests are available that can detect the early IgM antibodies as well as the IgG antibodies that remain forever in those who have been exposed.

How is the sample collected for testing?

Your doctor will take a swab or scraping from a blister or sore in the genital area. A sample of cerebrospinal fluid (CSF) may be collected from the spinal column when meningitis or encephalitis is suspected. For antibody testing, a blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

HSV testing is used to detect the presence of the herpes simplex virus in those who have genital sores, encephalitis, and in newborns suspected of having neonatal herpes, a rare but serious condition in which herpes is contracted during birth. A pregnant woman who has been diagnosed with herpes may be monitored regularly prior to delivery to identify a reactivation of her infection, which would indicate the necessity for a caesarean section to avoid infecting the baby.

The primary methods of testing for the virus are the herpes culture and HSV DNA testing. Although it is not as sensitive, HSV antibody testing can be used to help diagnose an acute HSV infection if acute and convalescent blood samples are collected. The convalescent blood sample is collected several weeks after the acute sample, and HSV IgG antibody levels are compared to see if they have risen significantly, indicating a current infection. Antibody testing may also be used to screen certain populations, such as sexually active people, potential organ transplant recipients, and those with HIV/AIDS, for a previously contracted HSV infection.

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When is it ordered?

A herpes culture (or HSV DNA testing) may be ordered when a patient has a blister or vesicle on their genitals. HSV DNA testing is ordered when a patient has encephalitis that the doctor suspects may be caused by a virus. HSV testing may be ordered regularly when a pregnant woman has herpes. A mother and newborn may be tested for HSV when a baby shows signs of HSV infection, such as meningitis or skin lesions.

HSV antibody testing is ordered primarily when a patient is being screened for a previous exposure to HSV. Occasionally, acute and convalescent HSV antibody testing may be ordered when a current infection is suspected.

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What does the test result mean?

A positive herpes simplex culture or HSV DNA test from a vesicle scraping indicates an active HSV-1 or HSV-2 infection. A negative test result indicates that the herpes simplex virus was not isolated but does not definitely rule out the presence of virus. This is because if the specimen taken does not contain actively replicating virus or if the sample was not transported under optimum conditions, no viable virus may be detectable, resulting in a false negative result.

The presence of HSV-1 or HSV-2 IgM antibodies indicates an active or recent infection. HSV-1 or HSV-2 IgG antibodies indicate a previous infection. A significant increase in HSV IgG antibodies, measured by comparing acute and convalescent samples, indicates an active or recent infection. Negative HSV antibody results mean that it is unlikely that the person has been exposed to HSV or that the body has not had time to begin producing HSV antibodies.

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Is there anything else I should know?

The most serious, or life-threatening, HSV infections can occur in newborns who are infected during birth and in immunocompromised individuals. The lesions tend to be more extensive and persist longer than in individuals who have healthy immune systems.

Herpes can make people more susceptible to HIV infection. Likewise, it can make HIV-infected individuals more infectious. Infection with HSV can also increase HIV viral load. HSV-2 infection is a significant opportunistic infection in HIV-infected individuals; up to 90% of HIV-infected individuals are co-infected with HSV-2.

HSV, in combination with human papilloma virus (HPV) infection, has been associated with a higher risk of developing cervical cancer.

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Common Questions

1.  How can herpes be prevented?

Oral herpes (mouth sores, skin lesions in non-genital sites) can’t be prevented. Exposure occurs during everyday life. However, genital herpes can be prevented by avoiding sexual contact with someone who has an active herpes infection and through the use of condoms. For more information, visit American Social Health Association: Learn About Herpes.

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2.  Are there other types of herpes viruses besides HSV-1 and HSV-2?

Yes. There are over 25 viruses in the herpes family and at least 8 types that infect humans. These include herpes simplex virus types 1 and 2 discussed in this article as well as Varicella Zoster virus (VZV, HHV-3), associated with chickenpox and shingles, Epstein Barr virus (EBV, HHV4), which can cause infectious mononucleosis, Cytomegalovirus (CMV, HHV-5), human herpes virus 6 (HHV-6) and human herpes virus 7 (HHV-7), both associated with roseola in young children, and human herpes virus 8 (HHV-8), which has recently been discovered to be in tumors called Kaposi's Sarcoma (KS) that occur in those with AIDS.

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 1568-1569.

Centers for Disease Control and Prevention. Genital Herpes - CDC Fact Sheet. Available online at http://www.cdc.gov/std/Herpes/STDFact-Herpes.htm through http://www.cdc.gov. Accessed July 2009.

Hunt, Richard. Virology: Herpes Viruses (Chapter 11). Microbiology and Immunology On-line. University of South Carolina School of Medicine. Available online at http://pathmicro.med.sc.edu/virol/herpes.htm through http://pathmicro.med.sc.edu. Accessed July 2009.

Lifestyle from Yahoo Canada. Herpes virus - 8 types. Available online at http://health.lifestyle.yahoo.ca/channel_section_details.asp?text_id=1364&channel_id=1028&relation_id=22614 through http://health.lifestyle.yahoo.ca. Accessed July 2009.

Deborah Fornstrom, M.T. (ASCP). The Children's Hospital, Aurora, CO.

Kristi Lookner, M.T. (ASCP). The Children's Hospital, Aurora, CO.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

(2004 May 24, Updated). Genital Herpes. CDC, STD Facts & Information, National Center for HIV, STD and TB Prevention, Division of Sexually Transmitted Diseases [On-line information]. Available online at http://www.cdc.gov/std/Herpes/STDFact-Herpes.htm through http://www.cdc.gov.

Wener, K. (2004 February 3, Updated). Herpes genital (genital Herpes simplex). MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000857.htm.

(2004 May, Updated). Herpes: What It Is and How to Deal With It. AAFP familydoctor.org [On-line information]. Available online at http://familydoctor.org/x5050.xml.

(2003 November 21, Updated). Genital Herpes. NIAID Fact Sheet [On-line information]. Available online at http://www.niaid.nih.gov/factsheets/stdherp.htm through http://www.niaid.nih.gov.

(2004). Herpes Simplex Virus (HSV). ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_a281.jsp#1151353 through http://www.arup-lab.com.

(2003 August 07). Mayo Clinic Staff. Genital herpes. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/invoke.cfm?id=DS00179 through http://www.mayoclinic.com.

(2000 May 17). Herpes Simplex Virus DNA UltraRapid 24 hr turn around. Specialty Laboratories [On-line test information]. PDF available for download at http://www.specialtylabs.com/education/download_PDF/tn_1106.pdf through http://www.specialtylabs.com.

(2004). Sevall, J. and Blum, R. Herpes Simplex Viruses. Specialty Laboratories, Use and Interpretation of Laboratory Tests Books [On-line information]. Available online at http://www.specialtylabs.com/books/display.asp?id=367 through http://www.specialtylabs.com.

(2001). Herpes: Get the Facts. ASHA National Herpes Resource Center [On-line information]. Available online at http://www.ashastd.org/hrc/educate.html through http://www.ashastd.org.

(2004 May 24). Herpes More Prevalent Than Thought. MedlinePlus by UPI [On-line News]. Available online (until June 23 2004) at http://www.nlm.nih.gov/medlineplus/news/fullstory_17929.html.