Because the genital herpes sores may not be visible to the naked eye, a doctor or other health care worker may have to do several laboratory tests to try to prove that symptoms are caused by the herpes virus. A person may still have genital herpes, however, even if the laboratory tests do not show the virus in the body.
A blood test cannot show whether a person can infect another with the herpes virus. A blood test, however, can show if a person has been infected at any time with HSV. There are also newer blood tests that can tell whether a person has been infected with HSV 1 and/or 2.
Source: National Institute for Allergy and Infectious Diseases
