Herpes Simplex Viruses
Although oral herpes is typically known as cold sores or fever blisters, while genital herpes gets the distinction of the name "herpes," they're actually quite similar. Fifty percent of their DNA is the same [source: HHV-6 Foundation]. Oral herpes is herpes simplex 1 (HSV-1), while genital herpes is herpes simplex 2 (HSV-2).
Both HSV-1 and HSV-2 cause fluid-filled blisters or lesions, which carry virions, or infectious particles. These blisters last from a week to a month, becoming open sores that crust over with scabs. The outbreak following the initial infection (usually a few days to a few weeks afterward) is usually the worst -- the ones after that are less painful. Some people actually confuse their mild outbreaks with other skin conditions. Early after infection, some people experience prodrome, a tingling, itching feeling that occurs in an area where blisters will shortly develop.
The main difference between HSV-1 and HSV-2 is their preferred sites of transmission and infection. HSV-1 generally results from oral contact, and the blister outbreaks are contained to the lips, mouth and face. The infection lies in a cluster of nerve cells near the ear called the trigeminal ganglion. HSV-2 generally results from genital contact with blisters in the genitals, anus and inner thighs, and it lives in nerve cells in the sacral ganglion, near the base of the spine.
Many people believe that HSV-2 is more dangerous than HSV-1, but that's not true. In fact, some researchers argue that HSV-1 is more dangerous because it's more prevalent. Both types of herpes can cause fevers and swollen lymph nodes. Urinating can be extremely painful when having an outbreak of HSV-2 as the urine hits the open sores. HSV-1 infections can also spread to the eyes (herpes keratitis), face and chest (herpes gladiatorum), and fingers and thumbs (herpetic Whitlow). In rare cases, it can spread to the brain and cause herpes encephalitis or Molliet's meningitis, types of brain inflammation that can result in death. There has been some research associating herpes simplex viruses with Alzheimer's and Bell's palsy, although definitive links haven't yet been proved.
Next, we'll look at how the herpes simplex viruses are spread and how their symptoms can be treated.