Herpes simplex virus (HSV) is a common virus that belongs to the herpesvirus family. There are two main types of HSV: HSV-1 and HSV-2. Both types can cause similar symptoms, including painful blisters or sores, although HSV-1 typically causes sores around the mouth (cold sores), while HSV-2 usually causes genital herpes. Once infected, the virus can remain dormant (inactive) in the body and may reactivate periodically, leading to new outbreaks.
How is herpes simplex virus spread?
HSV spreads primarily through direct contact with infected skin, saliva, or bodily fluids. HSV-1 is usually transmitted through oral contact, such as kissing or sharing utensils. HSV-2 is primarily transmitted through sexual contact. However, both types can spread to other parts of the body through skin-to-skin contact. It is possible to transmit the virus even when no visible symptoms or sores are present.
What diseases are associated with herpes simplex virus?
HSV can cause several medical conditions, including:
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Cold sores (oral herpes): Painful blisters typically around the lips and mouth, most commonly caused by HSV-1.
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Genital herpes: Painful blisters or ulcers in the genital area, usually caused by HSV-2 but occasionally by HSV-1.
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Herpetic whitlow: Infection of the fingers, resulting in painful blisters, common among healthcare workers.
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Herpes keratitis: An infection of the eye that can lead to vision problems or blindness if not treated promptly.
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Neonatal herpes: A serious infection in newborn babies acquired during childbirth from an infected mother.
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Encephalitis or meningitis: Rare but severe infections of the brain or surrounding tissues.
Can herpes simplex virus cause cancer?
No, herpes simplex virus itself is not known to cause cancer. Unlike some other viruses in the herpes family (such as human herpesvirus-8 and Epstein-Barr virus), HSV is not associated with cancer development.
How do pathologists test for herpes simplex virus?
Pathologists commonly use the following tests to detect HSV:
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Microscopic examination: Pathologists can examine tissue samples stained with special techniques to identify cells infected by HSV. Infected cells are often described as showing viral cytopathic effects.
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Immunohistochemistry (IHC): A test that uses specific antibodies to detect viral proteins, making infected cells visible under a microscope.
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Molecular tests: Polymerase chain reaction (PCR) is a highly sensitive test that detects the genetic material (DNA) of HSV. PCR can confirm infection even when symptoms are mild or not apparent.
How do pathologists interpret the results?
When HSV infection is present, pathologists observe characteristic changes in the infected cells, including multinucleated giant cells, nuclear enlargement, and inclusions within the nucleus. Together, these changes are collectively referred to as viral cytopathic effects.
A positive immunohistochemistry result means that HSV proteins have been detected in the cells. A positive PCR test result indicates that HSV DNA is present, confirming active or recent infection. Negative results typically mean HSV infection is not involved. Pathologists use these results, along with clinical findings, to help diagnose HSV-related conditions.
