Herpes Simplex Virus 1 and 2 (HSV-1 and HSV-2) are two species of the herpes virus family, Herpesviridae, which might cause life-long infections. The herpes simplex viruses have a tropism for skin (where they cause vesicles), the mucosae (gingivostomatitis and genital herpes), the eye (conjunctivitis and keratitis) and the central nervous system (meningitis and meningoencephalitis). Primary infection is often asymptomatic or atypical but subsequently the virus can persist in the body in a latent state. Reactivation often but not always takes the form of the classic "cold sore". Congenital herpes is dangerous for newborns but it can occur if the mother has a genital eruption during pregnancy or delivery (especially if the infection is a primary one). Serological analysis can be used to diagnose primary infection by demonstrating either seroconversion or the presence of IgM antibodies. Later, IgG antibodies persist for a long time and their levels do not significantly change during reactivation or recrudescence. Once someone has been infected with HSV, they will continue to produce small quantities of HSV IgG antibodies. See Herpes Simplex Virus Type I & II DNA (HSV I & II), PCR