The World Health Organization (WHO) has updated its fact sheet on Herpes Simplex Virus (herpes).

This article will present details regarding Herpes Simplex Virus type 1 (HSV-1).

Background Information:

Infection with the herpes simplex virus, commonly known as herpes, can be due to either herpes simplex virus type 1 (HSV-1) or herpes simplex virus type 2 (HSV-2).

HSV-1 is mainly transmitted by oral to oral contact to cause infection in or around the mouth (oral herpes). However, HSV-1 can also be transmitted to the genital area through oral-genital contact to cause genital herpes.

HSV-2 is almost exclusively sexually transmitted, causing infection in the genital or anal area (genital herpes).

Key Messages:

Most HSV-1 infections are acquired during childhood, and infection is lifelong.

The vast majority of HSV-1 infections are oral herpes (infections in or around the mouth, sometimes called orolabial, oral-labial or oral-facial herpes), but a proportion of HSV-1 infections are genital herpes (infections in the genital or anal area).

Magnitude of the Problem 

In 2012, an estimated 3.7 billion people under the age of 50, or 67% of the population, had HSV-1 infection.

Estimated prevalence of the infection was highest in Africa (87%) and lowest in the Americas (40-50%).

140 million people aged 15-49-years were estimated to have genital HSV-1 infection worldwide in 2012, but prevalence varied substantially by region.

In Africa, most HSV-1 infections are acquired in childhood, before the age of sexual debut. However, in the Americas, Europe and Western Pacific, HSV-1 continues to be acquired well into adulthood.

Signs and symptoms

Oral herpes infection is mostly asymptomatic, and the majority of people with HSV-1 infection are unaware they are infected.

Symptoms of oral herpes include painful blisters or open sores called ulcers in or around the mouth. Sores on the lips are commonly referred to as “cold sores.” Infected persons will often experience a tingling, itching or burning sensation around their mouth, before the appearance of sores. After initial infection, the blisters or ulcers can periodically recur.

Genital herpes caused by HSV-1 can be asymptomatic or can have mild symptoms that go unrecognized.

When symptoms do occur, genital herpes is characterised by 1 or more genital or anal blisters or ulcers. After an initial genital herpes episode, which may be severe, symptoms may recur, but genital herpes caused by HSV-1 often does not recur frequently.

Transmission

HSV-1 is mainly transmitted by oral-to-oral contact to cause oral herpes infection, via contact with the HSV-1 virus in

• sores,
• saliva, and
• surfaces in or around the mouth.

HSV-1 can also be transmitted to the genital area through oral-genital contact to cause genital herpes.

The greatest risk of transmission is when there are active sores.

In rare circumstances, HSV-1 infection can be transmitted from a mother with genital HSV-1 infection to her infant during delivery.

Individuals who already have HSV-1 oral herpes infection are unlikely to be subsequently infected with HSV-1 in the genital area.

Possible complications

• Severe disease (in immunocompromised individuals)
• Neonatal herpes (when an infant is exposed to HSV in the mother’s genital tract during delivery)
• Psychosocial impact

Treatment

Antiviral medications (such as acyclovir, famciclovir, and valacyclovir) can help to reduce the severity and frequency of symptoms, but cannot cure the infection.

Prevention

People with active symptoms of oral herpes should

• avoid oral contact with others
• sharing objects that have contact with saliva 
• abstain from oral sex

Individuals with symptoms of genital herpes should abstain from sexual activity whilst experiencing any of the symptoms.

The consistent and correct use of condoms can help to prevent the spread of genital herpes.

Pregnant women with symptoms of genital herpes should inform their health care providers. Preventing acquisition of a new genital herpes infection is particularly important for women in late pregnancy, as this is when the risk for neonatal herpes is greatest.

Several candidate HSV vaccines are currently being studied.

Useful Links:

Link to the updated fact sheet:

http://www.who.int/mediacentre/factsheets/fs400/en/

Link to WHO brochure on sexually transmitted infections (English) [PDF]:

http://apps.who.int/iris/bitstream/10665/82207/1/WHO_RHR_13.02_eng.pdf?ua=1