Herpesvirus 6 Antibodies (IgG, IgM) - HHV-6 is a distinct herpes virus that typically causes a self-limiting illness in patients who are not immunocompromised. In some patients, especially if immumocompromised, HHV-6 can cause febrile convulsions in infants, encephalitis mononucleosis-like symptoms, and hepatitis.