Herpes virus covers a large variaty of human diseases, and they are under the Herpesviridae family. Some of the virus from the family Herpesviridae are:
- Herpes simplex virus type 1 (HSV-1; species Human herpesvirus 1)
- Herpes simplex virus type 2 (HSV-2; species Human herpesvirus 2)
- Varicella Zoster virus (VZV; also known as Human Herpesvirus 3 - HHV3)
- Epstein-Barr virus (EBV; species Human herpesvirus 4)
- Human herpes virus 6 (HHV-6)
There are other species in the family Herpesviridae, but here we will focus in the first and second from the list above : HSV-1 and HSV-2
Herpes simplex virus is a double stranded DNA virus that cause a common infection in humans. This infection is characterized by small watery blisters around lips and genital. The structure of this virus is an icosahedral capside and has an envelop. The genome encode approximatelly 100 proteins. Take a look below how the virus looks like:
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| By Bryan Brandenburg, March 9, 2013. (From http://bryanmbrandenburg.com/herpes-simplex-virus-3d-animation/) |
How the virus develop the lesions is explained in chapter 38 (Human diseases caused by viruses and prions) of Prescott's Microbiology p.871:
"The herpesvirus genome must first enter an epitelial cell for the initiation of infection. The initial association is between proteoglycans of the epithelial cell surface and viral glycoproteins. This is followed by a specific interaction with one of several cellular receptors collectively termed HVEMs for herpesvirus entry mediators. The capside, along with some associated proteins, then migrates along the cellular microtubule transport machinery to nuclear envelope pores. This 'docking' is thought to result in the viral DNA being injected through the nuclear envelope pores while the capsid remains in the cytoplasm."
Since the virus starts being multiplied, the host cell metabolism is inhibited and the cell induces itself to apoptosis. This way the cell dies and new amounts of virus are released to infect new cells. Following we have an image of how the watery blisters looks like:
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| (From: http://www.edoctoronline.com/media/19/photos_Herpes_Labialis_25036.jpg) |
The transmission occurs by direct contact person to person, and initially was thought that HSV-1 infected most lips and oral mucosa and HSV-2 infected most genitals. Nonetheless, both virues can infect either tissue site. Once a person is infected with these viruses, he/she will be a host for lifetime, because our organism is not capable to eliminate the virus. It gets housed in trigeminal nerve ganglion.
Conditions like emotional stress, excessive sunlight, fever, trauma, chilling and hormonal changes can reactivate the virus. Once reactivated, the virus moves from the nerve ganglion down a peripheral nerve and back to epithelial cells to produce the active phase.
In United States, 70 to 90% of adults have been infected by type 1 herpes. The diagnosis can be made by ELISA and direct fluorescence antibody screening of tissue. There is no cure, but the control can be made using antiviral drugs like acyclovir and famciclovir.
For now this is it!
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| (From |
Prescott's Microbiology, McGraw-Hill Science/Engineering/Math; 9 edition (January 8, 2013)
