What is Herpes Simplex Virus (HSV)? Causes, Symptoms and Treatment

What is herpes simplex virus?

Herpes simplex virus (HSV) is a lifelong viral infection that causes outbreaks of small, painful blisters on the skin and mucous membranes. There are two main types:

• HSV-1: Typically responsible for oral herpes, causing cold sores (herpes labialis) around the mouth and lips. HSV-1 is extremely common and is most often transmitted in childhood through kissing or touching.
• HSV-2: Primarily associated with genital herpes, causing outbreaks on the genitals or surrounding areas. HSV-2 is transmitted almost exclusively through sexual contact.

It is important to understand that HSV is not a reflection of poor hygiene or promiscuous behaviour. The virus is highly contagious and can be transmitted by people who do not know they are infected.

What does an HSV outbreak look like?

An outbreak typically follows a predictable pattern. Many people experience warning symptoms before the blisters appear:

Prodromal phase (warning symptoms)

The outbreak typically begins with tingling, burning, itching or numbness in the affected area — often 1–2 days before the blisters appear. Some people also experience local tenderness or swollen lymph nodes.

Blister phase

Clusters of small, fluid-filled blisters then appear on a reddened base. The blisters are typically painful. With HSV-1 they usually form at the corner of the mouth or on the lips; with HSV-2 on or around the genitals, buttocks or thighs.

Healing phase

The blisters burst and form ulcers, which are subsequently covered by a crust. Symptoms usually clear within 2–4 weeks during the first outbreak and more quickly during subsequent outbreaks. The skin usually heals without scarring.

Why does it happen — and what triggers outbreaks?

HSV spreads through direct contact with infected skin or bodily fluids. The virus penetrates the skin or mucous membranes and then establishes itself in sensory nerve cells near the spinal cord, where it remains dormant (latent) for life. Certain factors can reactivate the virus and trigger a new outbreak:

• Stress and fatigue: Psychological or physical stress is one of the most common triggers.
• Weakened immune system: Illness, medication (e.g. immunosuppressants) or HIV can increase the frequency of outbreaks.
• Sunlight (UV radiation): Prolonged sun exposure is a well-known trigger for cold sores (HSV-1).
• Hormonal changes: Menstruation can trigger HSV-2 outbreaks in women.
• Febrile illness: Colds, influenza and other infections can reactivate the virus.

Asymptomatic transmission is also possible: the virus can shed from the skin (viral shedding) even without visible blisters, which is why HSV can be transmitted even when there are no visible signs of an outbreak.

Who gets HSV?

HSV is extremely widespread globally:

• HSV-1: The WHO estimates that approximately 67% of the global population under 50 is infected with HSV-1. Most are infected in childhood and never experience symptoms.
• HSV-2: Approximately 11% of the global population under 50 carries HSV-2. Prevalence is higher in women than men.

Many infected individuals never experience noticeable symptoms, or only notice mild signs that they attribute to other causes. HSV can therefore be carried and spread unknowingly.

Treatment and management of HSV

There is currently no cure for HSV — the virus remains in the body for life. However, antiviral medications can shorten outbreaks, reduce symptoms and lower the risk of transmission:

Frequently asked questions