Understanding How the Herpes Simplex Virus Works

The Science of Cold Sores and Genital Herpes

Herpes, cold sore or fever blister
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The herpes virus is a common viral infection and one of the most difficult to control. The word "herpes" itself is derived from the Greek word herpein, which means "to creep."

Herpes simplex viruses are double-stranded DNA viruses with two very different strains:

  • herpes simplex virus type 1 (HSV-1)
  • herpes simplex virus type 2 (HSV-2)

HSV-1, or oral herpes, is responsible for the majority of cold sores.

HSV-2, by contrast, causes genital herpes, primarily on the vagina or anus.

According to the World Health Organization (WHO), around 417 million people are living with HSV-2 worldwide, while just under 3.5 billion people under age 50 experience an episode of HSV-1 each year.

Previously it was believed that HSV-1 infections occur only in the mouth and that HSV-2 infections only occur in the genital area. It has now been shown that either virus can infect either site. Moreover, a person can be infected with both viruses, making some outbreaks all the more tricky to diagnose.

How the Herpes Simplex Virus Works

The herpes virus spreads when it comes into contact with broken skin or with tissues of the mouth, vagina, or anus. Once it enters a cell, it penetrates nucleus and begins the processes of replication. At this stage, even though cells are infected, most people will not experience any symptoms.

During the initial infection, the virus is transported through nerve cells to nerve branching points, known as ganglia. It is there that the virus will stay in an inactive, dormant state, neither replicating nor causing any symptoms.

On occasion, the dormant virus will suddenly reactivate, starting the replication process anew.

When this happens, the virus will travel back through the nerve to the surface of the skin. In the process, many of the infected skin cells will be killed, causing blisters to form.The eruption of these blisters creates the characteristic ulcers we come to recognize as cold sores or genital herpes.

While herpes is most contagious when ulcers are open and oozing, it can also be spread when sores are not present. The sharing of beverages, towels, and kissing can easily transmit HSV-1. HSV-2 is most typically spread through sexual contact.

Cause of a Herpes Recurrence

Certain triggers can cause the herpes virus to reactive. This is known as a recurrence and can happen even in persons who have normal immune systems. There are a number of known triggers that can stimulate recurrence:

  • physical stress
  • poor emotional coping style
  • persistent stresses for greater than one week
  • anxiety
  • viral infection
  • fever
  • exposure to ultraviolet light, heat, or cold
  • nerve damage
  • tissue damage
  • changes in immune function
  • hormonal changes, such as during menstruation
  • fatigue

Symptoms of a Herpes Outbreak

The herpes simplex virus is generally asymptomatic, meaning that many people infected with the virus are not even aware they have it.

When symptoms do appear, they usually do so quickly and can sometimes take as many as two to three weeks to get better.

Symptoms of HSV-1 include:

  • tingling, burning sensation around the mouth
  • cold sores (also known as fever blisters)

Symptoms of genital herpes, HSV-2, include:

A Word From Verywell

If you believe you are developing a cold sore or genital herpes, speak with your doctor or clinic.There ae antiviral medications that may not be able to stop an infection from happening, but it may reduce the pain and duration of an outbreak.

Early intervention is key.


  • Centers for Disease Control and Prevention (CDC). "Sexually Transmitted Diseases Treatment Guidelines, 2006." Morbidity and Mortality Weekly Report. 55(2006): 16-20.
  • Habif, Thomas. "Warts, Herpes Simplex, and Other Viral Infections." Clinical Dermatology, 4th Edition. Ed. Thomas Habif, MD. New York: Mosby, 2004. 381-388.
  • Yeung-Yue, Kimberly. "Herpes simplex viruses 1 and 2." Dermatologic Clinics. 2002; 20:1-21.