Dear An: Your question is excellent. Generally IgM antibodies to herpes simplex virus (HSV) suggest a recent infection. IgG antibodies to HSV appear later, last longer and are thus a marker for a past infection. One of the problems with such nonspecific tests is that they cannot tell for sure if it is type1 HSV (commonly called oral) or type 2 HSV (commonly called genital). There are newer tests (eg HerpeSelect) which can make this diagnosis.
Here is a direct quote about this issue with a link to the entire citation:
A positive herpes IgG test, if the test result is accurate, means that your body has been infected with the herpes simplex virus. Type specific herpes IgG tests can often distinguish between HSV-1 and HSV-2, but they can not detect whether a particular infection is oral or genital in the absence of symptoms. HSV-1 usually infects the mouth, causing oral herpes, and HSV-2 usually infects the genitals, but either virus can infect either location. Herpes IgG and IgM tests can only tell you that you have been infected, not where.
http://std.about.com/od/herpes/f/Positive-Herpes-Igg-Test.htm If your MD did do a type specific IgG, they would be able to tell you if they requested IgG testing for type 1 or type 2. Also, your MD should be able to give you an understandable explanation of your lab results
If it's any consolation about 16% of US citizens will test positive for HSV type 2--with higher numbers in women.
Yours,
Jane