This is an IFA (indirect fluorescent antibody) IgM & IgG type of test and now the one to use in search of acute infection (especially in newborns, infants & children where concern for systemic illness). A high percentage of adults are seropositive;  the "fever blister" virus...a DNA virus of the herpes group. This HSV I virus is closely related to HSV II, the "genital herpes" virus. In late 2004, a new serum test came out as a suppliment or alternative to the IFA test for adults, hoping to more clearly differentiate HSV I & HSV II chronic status.

HSV I tends to recurr at a rate of once per year or less, while HSV II has a much more frequent recurrence rate. Both produce painful blisters and ulcerations, and the virus can be dormant in the location and erupt and re-erupt with sores (DFA smear tests or Tzank smears can be done from such sores or blisters).

Since about 1990, there are antiviral agents which may cure an initial or recurrent infection if caught and treated very early; cures are less likely once established, though treatment make help decrease the severity.

Since oral sex has become so prevalent in modern times, the differentiation between an infection with HSV I and HSV II is less reliable for purposes of blaming an etiology. That is, a person could engage in oral sex with one partner and acquire HSV II from that infected partner. The person may or may not have an obvious sore (cold sore or fever blister) to indicate having caught the disease; then, through kissing only, that person may pass the HSV II on to another person who has not engaged in any sort of genital sex. That is, it is possible for a righteous virgin to get HSV II of the lips or mouth.

In IFA testing, there can be serious test cross-reactions so that a person appears to be positive for both HSV I and HSV II when only having been exposed to one of the agents. The agent with detectible presence of IgM (acute) antibody (Ab) and/or the agent with the highest level of IgG (immune) Ab is likely the actual offending organism in an active infection. [ warning]

• Less that 20% of adults; about 80% of adults have detectable IgG.
• previously infected persons who did not mount a detectible level of Ab (may or may not be "immune")
• previously infected persons who have become seriously immunocompromised and cannot produce detectible Ab

 Elevated, reactive, or positive IFA results:

• HSV I infection

• HSV II cross-reaction

Other names for this exact or approximate agent are:   

• Herpes simplex virus I

(posted 2000; latest update 22 December 2004)