Herpes simplex virus

General Information

The Herpes simplex virus (HSV) is categorised into 2 types: HSV-1 and HSV-2.

Like varicella-zoster virus, latent HSV infection can re-activate and lead to recurrent outbreaks of symptoms.

Transmission

HSV-1 is mainly transmitted by oral-to-oral contact, causing oral herpes (including symptoms known as cold sores), but it can also lead to genital herpes.

HSV-2 is a sexually transmitted infection that causes genital herpes.

Symptoms

HSV-1 can cause oral herpes. Both types of HSV can cause genital herpes and an eye infection (Herpes simplex ophthalmicus) which can lead to blinding complications.

Most HSV infections are asymptomatic, but symptoms of herpes include painful blisters or ulcers that can recur over time.

Epidemiology

An estimated 3.7 billion people under age 50 (67%) have HSV-1 infection globally.

An estimated 491 million people aged 15–49 (13%) worldwide have HSV-2 infection.

Vaccines Pipeline

1
Vaccines in
the pipeline

IMMUNISATION TECHNOLOGY

mRNA (1)

DEVELOPMENT PHASES

Phase II (1)

TRIAL POPULATION

Adults (1)

Source:
WHO. Herpes Simplex Virus. 2023. Available from: https://www.who.int/news-room/fact-sheets/detail/herpes-simplex-virus.
Kanukollu BM, Patel BC. Herpes Simplex Ophthalmicus.. StatPearls Publishing. 2022.
[Accessed: August 2025]