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Herpes Simplex A024

Last amended 
19 November 2019
Current RMA Instruments

Reasonable Hypothesis SOP

39 of 2018

Balance of Probabilities SOP

40 of 2018

Changes from previous Instruments

SOP Bulletin 202

ICD Coding
  • ICD-9-CM Codes: 054
  • ICD-10-AM Codes: A60, B00
Brief description

This SOP covers clinical infection with the Herpes simplex virus (HSV) types 1 and 2.  This infection usually manifests as episodes of localised vesicular eruptions on the skin or mucus membranes.  The typical sites of eruptions are the orofacial area and the genital area, but lesions can occur at other sites.  Eruptions can be painful and typically last for 10 to 14 days for an initial episode and around 5 days for recurrences.

Confirming the diagnosis

HSV infection can be asymptomatic.  The SOP definition requires a clinical illness to have occurred. The diagnosis of HSV infection may be suspected on clinical grounds but should be confirmed by laboratory testing (viral culture, serology, immunofluorescence or polymerase chain reaction assay).  The diagnosis can be made by a treating GP.

The relevant medical specialist is an infectious diseases physician.

Additional diagnoses covered by SOP
  • Cold sores
  • Genital herpes
  • Herpes gladiatorum
  • Herpes labialis
  • Herpes simplex encephalitis
  • Herpes simplex retinal necrosis
  • Herpetic whitlow
  • Oral-facial herpes
Conditions not covered by SOP
  • Herpes zoster*

* another SOP applies

Clinical onset

Clinical onset may be difficult to determine and there may be more than one clinical onset.  Both infections are common.  Initial infection may cause a significant clinical illness but it may also be asymptomatic or go unrecognised (e.g. HSV-1 pharyngitis may be mistaken for a bacterial pharyngitis).  HSV-1 is more common and tends to be acquired earlier, via contact with oral secretions.  HSV-2 is usually acquired from sexual contact.  Both infections tend to cause recurrent clinical episodes, particularly in the first year after infection.

HSV-1 typically causes oral-facial infection.  Recurrent episodes most commonly involve the lips (cold sores). HSV-2 typically causes genital infection.  However, both may affect either site and both may manifest at other sites.  Infection may remain dormant for many years then be reactivated by some trigger factor.

Both infections may occur in one person.  Whether a new clinical episode is a recurrence or a new infection with the other HSV type may be difficult to determine.  In such cases medical advice should be sought. 

Clinical worsening

Clinical worsening may be evidenced by reactivation of quiescent disease or by the development of complications, such as eczema herpeticum.