Thanks for your concern about genital herpes. It is caused by Herpes Simplex Virus of two types- HSV Type 1 and HSV type 2. It will cause an outbreak, normally within 3 weeks from having sex with infected people. It is associated with painful groups of blisters in groins, genitals or in mouth and lips if it is oral herpes or herpes labialis. Usually, while having an outbreak or similar herpes like blisters, fluid from the blister is sent for medical examination for find whether it is caused by herpes simplex virus. If you haven’t had an outbreak, blood is used to test the presence of virus. But this is not a assured test. Moreover, a negative test result from fluid tests of blisters is not as reliable as a positive test result. Anyway, fluid test is found to be one of the most assured test to find out the infection. But in some stages of blisters like at the time of crust formation, it may give false negative tests as the viral infection may have got dried up. Cultures of sore fluids taken during the time of first outbreak is considered to be the most reliable one to find a positive result. Blood tests are also out there to find herpes infection. These tests are used to determine the presence of antibodies in human body. There are specific tests for HSV type 1 and HSV type 2. There are also some expensive tests like PCR test which is also called Polymerase Chain Reaction test which is considered as one of the most reliable tests for HSV. It can identify genetic material of virus. Another test is the rapid fluorescent antibody screening test which is used to find the HSV presence in laboratories. Hope my answer was helpful Take care.