Herpes Simplex Virus

Initial mucocutaneaous infection with HSV-1 or HSV-2 is followed by latent infection of neuromnal cells in the dorsal root ganglia, and the potential for reactiviation and viral excretion (although usually asymptomatic).

Promary HSV-1 or HSV-2 infection is also often asyumptomatic (although viral shedding ocurrs and patients are infectious), and most individuals do not experience symptoimatic recurrence. Previous infection with HSV-1 (and immunity) does not prevent subsequent infection with HSV-2, but may reduce the severity of HSV-2 infectoin. neonatal infection ocurrs by exposure of the infant to virus excreted by the infected mother at vaginal delivery.

HSV-1 is the usual cause of oro-facial herpes infections while most genital herpes infections (and nearly all recurrences) are caused by HSV-2.

Direct Testing (DFA and Viral Culture) is indicated in active infections, but requires accurate collection of specimens from lesions and so cannot be used for asymptomatic genital herpes infections.

Specimens:

• DFA: Collect infected cells from the base of the vesicle or ulcer using an HSV DFA collection kit.
• Viral Culture: collect infectec cells and vesicle fluid using a viral transport swab

Request: 'HSV DFA' and/or 'HSV culture'
Note: if DFA is positive, no further testing is required; if DFA is negative and a viral transport swab has been collected, viral culture will be performed.

Anti-HSV IgG is usually detectable 2-4 weeks after primary infection. Specific IgM is detectable in primary infections, but may also ocurr in reactivation and so is not diagnostically helpful. Serology is not recommended for the diagnosis of acute HSV infections.

However type specific HSV IgG serology for immune status may be useful for:

• Epidemiology and couselling for 'in contact' or 'at-risk' patients.
• classification of HSV immune status in patients with gential blisters or ulcers which are culture negative
• prognosis (eg HSV-1 genital infectoin is not as likely to recur as HSV-2 infection)

Specimen: Serum (gold top) tube
Request: 'HSV 1/2 IgG'

Further information may be obtained from the Australian Herpes Management Forum website: www.herpes.on.net