At a Glance
Why Get Tested?
To screen for or diagnose infection with the herpes simplex virus (HSV)
When to Get Tested?
If you have symptoms of an infection with HSV, such as blisters in the genital area, or symptoms of viral meningitis; if you have certain risk factors
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 virus 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 : 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 Sexual Health Association and its Herpes Resource Center, about 50% of adults in the U.S. have HSV-1 and about 17% have HSV-2. Because symptoms may be mild, however, 90% of those who have HSV-2 may be unaware that they have been infected.
When someone is first infected, the person may have obvious and painful blisters at the site of infection, which usually appear within two weeks after the virus is transmitted. The lesions generally 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 such as 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, the person will harbor the HSV in a latent form. During periods of stress or illness, the virus may reactivate.
People 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 can suppress outbreaks and shorten the duration of symptoms and active shedding of virus.
Rarely, the virus can cause neonatal herpes when a woman transmits the virus to her baby during a vaginal delivery. Neonatal herpes symptoms appear during the first month of life and, if left untreated, can cause long-term damage to a baby's health. 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 herpes simplex virus can be transmitted to the brain, causing encephalitis. This illness can be fatal or cause serious, permanent neurological problems in those who survive.
HSV testing detects 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 via swab from an open sore and inoculated into cells that allow the virus to grow. Once the the virus is detected, it can be further Identified as HSV-1 or HSV-2, which may be useful for prognosis. This test is sensitive and specific, but it takes two or more days to complete. False negatives can occur if there is not enough active virus in the test sample, which can occur if the lesion is cultured more than 48 hours after the symptoms appear.
- HSV DNA testing or HSV PCR. This method detects HSV genetic material in a patient's sample from the blister, blood, or other fluid, such as spinal fluid. DNA testing is usually done only if the culture is negative but the practitioner still suspects herpes, or if the patient has received treatment for herpes. This method can detect the virus as well as identify the type of herpes virus. Because this test is more sensitive than culture, : it is useful 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 (inflammation of the cornea).
- 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, slowly decline, 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 health care practitioner 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.
How is it used?
HSV testing is used to detect the presence of the herpes simplex virus (HSV) in those who have genital sores or encephalitis : and in newborns suspected of having neonatal herpes, a rare but serious condition in which herpes is contracted during vaginal birth.
The primary methods of testing for the virus are the herpes culture and HSV DNA testing (PCR). 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.
When is it ordered?
A herpes culture (or HSV DNA testing) may be ordered when someone has a blister or vesicle on their genitals.
HSV DNA testing is ordered when a person 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 that could be caused by the herpes virus.
HSV antibody testing is ordered primarily when someone 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.
A doctor may also order an HSV antibody test if someone has another STD and is at risk for the infection. Risk factors include having multiple sex partners, having a sex partner with herpes, being infected with HIV, or being at risk for HIV because the person is a man who has sex with men.
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. 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.
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.
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 the American Sexual Health Association's Herpes Resource Center.
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, HHV-4), 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.