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Herpes Simplex

Epidemiology of Infectious Diseases: Herpes Simplex

Causal agent
Two serotypes of herpes simplex virus have been identified. Herpes simplex virus type 1 (HSV-1) and Herpes simplex virus type 2 (HSV-2).

Common clinical features
Infection with HSV is characterized by a localised primary infection, latency and recurrence1.

Herpes simplex virus type 1 (HSV-1) is typically associated with gingivostomatitis1

Herpes simplex virus type 2 (HSV-2) is sexually transmitted. Symptoms include genital ulcers or sores. The virus may also lead to meningoencephalitis or cause infection of the eye. 

Both HSV-1 and HSV-2 can affect the genital tract and HSV-2 can cause primary infection of the mouth1.

Complications include eczema herpeticum, Bell's Palsy, encephalitis, meningitis, ocular herpes and erythema multiforme1.


  • Worldwide 50-90% of adults possess circulating antibodies against HSV-1 and initial infection usually occurs before age 5. There is also a secondary peak among young adults1,2.
  • HSV-2 infection usually begins with sexual activity and is rare before adolescence2.
  • Genital herpes simplex virus infection is the most common ulcerative sexually transmitted disease in the UK (Health Protection Agency).
  • In 2004, 18,991 new cases were diagnosed in the UK with the highest rates observed among young adults aged 20-24 years (Health Protection Agency).


Mode of transmission
Direct contact with oral secretions.

Unprotected vaginal or anal sex, genital contact or through oral sex. 

Incubation period
1-6 days. The virus may be shed in the saliva for 1-8 weeks after primary infection and for about 3 days in recurrent infections2.

Period of Communicability
HSV can be isolated for 2 weeks and up to 7 weeks after primary infection. HSV may be shed intermittently for years and possible lifelong in the presence or absence of clinical manifestations2.

Oral antivirals for primary infection and reactivation.

Topical antivirals may be used for reactivation1.

Prevention and control
Sunscreen and oral antiviral may be considered to prevent reactivation1.

Personal hygiene to limit spread.


  1. Hawker J, Begg N, Blair I, Reintjes R, Weinberg J. Communicable Disease Control Handbook, Blackwell, 2005.
  2. Heymann D L, editor, Control of Communicable Disease Manual. 18th ed. American Public Health Association; 2004.

© CM Kirwan 2006