How effective is STI screening for genital herpes?

A clinician may collect fluid from a new genital sore for laboratory testing. This can identify herpes virus at the affected site, but a sample is harder to interpret after a sore has crusted or started healing. A negative swab does not always rule out infection if the lesion was old, the sample was difficult to collect, or no sore was present.

Blood testing looks for antibodies made after exposure to herpes simplex virus. It may help in selected situations, such as recurrent symptoms without a testable sore, but it cannot reliably show when infection happened or who transmitted it. It also does not show whether symptoms at a particular site are caused by herpes.

If you notice a new blister, ulcer, burning area, or grouped sores, arrange assessment promptly while the area is still fresh. Avoid sexual contact until you have been assessed, because skin-to-skin spread can occur even when symptoms are subtle. Do not apply creams that hide the lesion before the appointment unless a clinician has advised them.

Tell the clinician when the symptoms began, whether they have returned, and whether a partner has symptoms or a known diagnosis. Ask which test fits your situation and whether screening for other STIs is appropriate.

Seek prompt medical care for painful genital sores, difficulty passing urine, fever with a new rash, or symptoms during pregnancy. Newborn exposure around delivery can be serious, so pregnancy and possible genital herpes need direct clinical advice. Seek urgent help if severe illness, confusion, or rapidly worsening symptoms develop.

Ask whether a swab can be taken today, how the result will affect treatment, whether a blood test would add useful information, and how to reduce transmission while symptoms settle.