Herpes

What is being analysed?
Herpes simplex testing is carried out to identify an acute infection or to detect antibodies, which indicate past exposure to the virus.
Known as one of the most common causes of viral infection, herpes simplex virus (HSV) exists in two forms, HSV-1 and HSV-2. Both are contagious to humans and cause small blisters (cold sores) which, when they burst, form open sores that are a source of infection. HSV-1 mainly causes sores around and inside the mouth, while HSV-2 usually causes sores around the genital area.
The virus usually passes from person to person through contact, via the virus contained in the fluid of the blisters and released when the sores burst; more rarely, infection can come from people without symptoms, when the sores are not yet visible.
HSV-2 often behaves as a sexually transmitted disease, but HSV-1 can also be present in the genital area and be caught through oral sex. According to the American Social Health Association and the National Herpes Resource Center, in the UNITED STATES about 50-80% of adults have HSV-1 and about 20% have HSV-2. Because symptoms can be mild, 90% of those with HSV-2 may be unaware that they are infected.

In an infected person the primary infection may resolve, but HSV can remain latent and reactivate during periods of stress or illness. In most cases HSV episodes, whether primary or due to reactivation, are more of a nuisance than a threat to health, although the virus can cause a dreaded congenital infection, neonatal herpes, as well as diseases of the central nervous system such as herpes meningitis and encephalitis. These forms of HSV infection can be fatal or cause permanent neurological damage. Patients with conditions that suppress the immune system, such as HIV/AIDS or those taking immunosuppressant treatment after an organ transplant, are at greater risk of HSV infection and its most severe forms.

HSV tests can detect the virus itself, viral DNA or antibodies against the virus. During an acute primary infection or reactivation, the virus can be detected by culture.

• Culture: a sample of fluid collected from an open sore (the most common sample) is incubated in a culture medium suitable for growing and isolating the virus. This test is sensitive and specific, but takes two or more days to complete. Fresh sores are the best “material” for this type of test; viral replication decreases over time, and late attempts at isolation can give a false negative result. Once the virus has grown in culture, it is possible to determine whether it is HSV-2 or HSV-1
• Viral DNA testing: viral DNA testing detects the genetic material of the herpes virus in a sample taken from the patient. This method allows the virus to be typed and quantified and is preferable when there is little virus present, as in viral encephalitis, or when sores have been present for several days.
• HSV antibody testing: anti-HSV antibodies are specific immunoglobulins produced by the body and released into the bloodstream to contain and fight the infection. IgM antibody production begins several days after a primary HSV infection and can be detected in the blood a few weeks later. IgG antibody production begins after that of specific IgM antibodies. Antibody concentrations rise progressively in the first weeks and then, after peaking, fall to a stable level in the blood. Once a person has been infected with HSV, they will continue to produce small amounts of anti-HSV IgG antibodies.
The anti-HSV antibody test can detect both virus types (HSV-1 and HSV-2), and tests are available that can detect both IgM antibodies early in the disease and IgG antibodies, which remain for life in people who have been exposed to the virus.

How is the sample collected for testing?
For culture, a recent blister or sore in the mouth or genital area is scraped with a swab.
For viral DNA testing, as well as swab material, a sample of cerebrospinal fluid (CSF) may be collected by lumbar puncture if meningitis or encephalitis is suspected. Antibody testing is carried out on a blood sample from a vein

How is it used?
When is it requested?
What does the test result mean?
Is there anything else I should know?

How is it used?
HSV testing is used to detect the virus in people with genital blisters or sores or encephalitis, and in newborn babies suspected of having neonatal herpes (a rare but serious condition in which the baby catches the virus while passing through the birth canal during delivery).
A pregnant woman diagnosed with an acute or past genital herpes infection must be monitored regularly throughout pregnancy to detect any reactivation of the infection promptly; if this happens, a caesarean section is indicated to protect the baby from the risk of infection.
The methods of choice for detecting the virus are viral culture and DNA testing. Although less sensitive, antibody testing can help diagnose an acute HSV infection if it is carried out on serial samples, collected during the acute phase of the illness and a few weeks later, by showing a rise in antibody levels. Antibody testing can also be used to identify groups of people who have previously been infected, such as sexually active people, potential organ transplant recipients and those with HIV/AIDS.

When is it requested?
Culture or HSV DNA testing may be requested for a person with blisters or vesicles in the mouth or genital area and for a patient with symptoms of encephalitis thought to be of viral origin.
HSV testing is also indicated in the initial screening in pregnancy and must be repeated regularly throughout pregnancy when a woman is found to have an acute or past HSV infection.
Mother and baby must be tested for HSV when a baby shows typical signs of herpes infection at birth, such as meningitis or skin lesions. HSV antibody testing has more limited uses and is indicated mainly when it is necessary to check whether a patient has previously been exposed to the virus. When an active infection is suspected, measuring antibody levels in a sample collected during the acute phase and during subsequent recovery can confirm the diagnosis.

What does the test result mean?
A positive culture or the presence of HSV DNA in material obtained by “scraping” a blister indicates an active HSV-1 or HSV-2 infection. A negative result indicates that the virus has not been isolated or identified, but does not rule out infection. The sample may contain virus that is not actively replicating (as happens with material from an “old” sore), or may have been transported and stored in less than ideal conditions, inactivating the virus and giving a false negative result.
The presence of IgM antibodies to HSV-1 or HSV-2 indicates an active or recent infection, while IgG antibodies suggest past exposure/infection. However, a significant rise in specific IgG levels in two samples collected during and after a suspected acute viral illness suggests a current HSV infection.
A negative specific antibody result makes it unlikely that the patient has been exposed to HSV, although it cannot be ruled out that there is a “window period” after infection but before the production of specific antibodies that can be detected by the methods commonly used in virology laboratories.

Is there anything else I should know?
The most serious forms of herpes infection are those in newborn babies infected during delivery and in immunocompromised people. In the latter in particular, the sores tend to be more extensive and last longer than in people with a normal immune system.
HSV infection can increase the HIV viral load; moreover, HSV-2 infection is often present as an opportunistic infection in people with HIV, so much so that up to 90% of them are co-infected with HSV-2. Genital HSV infection, together with papillomavirus (HPV) infection, has been associated with a high risk of developing cervical cancer.

1. How is the herpes virus transmitted?
2. What are the symptoms of herpes infection?
3. How is it treated?
4. How can herpes infection be prevented?

1. How is the herpes virus transmitted?
HSV is transmitted through direct contact, which
includes kissing and sexual activity (vaginal, oral or anal sex); infection through contact between healthy skin and the active sores of an infected person is less common. Genital herpes is most easily caught through sex with people who have active sores in the genital area or who do not know they are infected, although transmission from infected people before symptoms appear cannot be ruled out.

2. What are the symptoms of herpes infection?
Many people infected with HSV may have no symptoms, while others, although they have symptoms, do not pay them due attention. The most typical symptom of primary infection is painful blisters at the site of infection. These appear within 15 days of infection and usually heal in two to four weeks. The blisters may appear in the vaginal area, on the penis, around the anus, on the buttocks or thighs with HSV-2 infection, or around the mouth, at the base of the nostrils or inside the mouth with HSV-1 infection. Sometimes, after initially disappearing, the sores may come back; at other times the local symptoms are accompanied by general symptoms such as fever and swollen lymph nodes. However, infections with no symptoms, or with symptoms so mild that they are mistaken for other conditions (e.g. boils or insect bites), are not uncommon. After the primary infection has resolved, the virus becomes dormant but persists in the body, and may remain so for life. In some people, however, as a result of other illnesses or severe physical and/or emotional stress, the virus can reactivate and the sores can return, although they tend to heal more quickly than the sores of the primary infection. Sometimes the virus can become active and contagious without noticeable sores. The virus persists for life, but the frequency and severity of recurrent episodes vary greatly from person to person.

3. How is it treated?
There is no cure for herpes infection; some medicines can reduce the frequency and duration of acute episodes.

4. How can herpes infection be prevented?
Oral herpes (sores in the mouth, skin sores outside the genital area) cannot be avoided. Exposure to the virus is continuous in everyday life. Genital herpes, on the other hand, can be prevented by using condoms or avoiding sexual contact with people who have an active infection.