HSV

HSV (Herpes simplex viruses) are ubiquitous among humans. Once acquired, HSV can remain latent and when reactivated may produce recurrent infections. Infection types include genital lesions, cold sores, pharyngitis, ocular keratitis, and encephalitis. HSV are classified type 1 or 2 according to their genetic and antigenic composition. Each type is associated with a pattern of infection (oral HSV 1 and genital HSV 2), however, the site of infection is not an accurate predictor of the virus type. For example, HSV 1 is now suspected to cause a significant proportion of primary genital herpes. Specific diagnosis of HSV infection is required for neonates, the immunocompromised and individuals suspected of having herpes encephalitis.

Transmission is generally through physical contact/fluid exchange. Asymptomatic patients act as a carriers for spread of the infection. For this reason diagnosis through serology is important.

Generally the incubation period is between 1 to 26 days from infection to clinical symptoms. Serological diagnosis is important to determine the type of HSV infection and identification of asymptomatic carriers.

Typing may have utility in (a) prognosis, since it has been reported that the recurrence rate of genital HSV 1 infection is less than that of genital HSV 2, (b) treatment, since it has been reported that the antiviral activity of chemotherapeutic agents can differ between the two HSV types, and (c) epidemiological research, where an association of HSV infection with other disease processes such as cervical carcinoma is being studied. Several laboratory methods of typing HSV have been reported, including among others ELISA and immunofluorescence

Virus isolation in tissue culture is routinely used for diagnosing HSV infections. While tissue culture amplifies small numbers of infectious organisms for detection, it requires special facilities and 1-7 days before a result can be reported. While culture has stood as a generally recognized reference method, recovery is recognized to be less than 100%. Direct examination of viral antigen obtained from lesions provides results more rapidly.