Laboratory diagnosis of herpes simplex virus type 1 and type 2 infections

Abstract

Herpes simplex virus (HSV) is known to infect several body sites. Most commonly HSV infection results in lesions around the mouth or in the genital area. Infection at these sites may also be subclinical. Over the past decade HSV has been increasingly recognized as an important cause of both mild and severe diseases in a wide range of patients. Two distinct types of HSV are known, HSV-1 and HSV-2, and many antigens are shared between the two. Infection with either type of virus can occur early in life, although infection with HSV-2 becomes common only after puberty. The most common manifestation of HSV-1 infection is the orofacial “fever blister,” while HSV-2 is most often responsible for genital lesions. 1,2 Either virus type can, however, cause disease in almost any site of the body and can recur frequently. This recurrence of disease from an inapparent or latent state makes HSV infection unique among the common viral infections. Mistakes in diagnosis of HSV infections based on clinical findings alone are not uncommon. Herpetic lesions have been confused with allergic reactions, drug reactions, and lesions due to other infectious agents. Besides the medical importance of HSV in special situations, the social impact of having “herpes” is of considerable concern is almost everyone. Therefore, precise diagnosis of HSV infection is of paramount importance, particularly since effective antiviral therapy is available for many forms of the disease. Morphologically, all herpesviruses are alike (Fig. 1); therefore, it is not possible to differentiate members of the group by their structure alone. Although rapid techniques for diagnosis of HSV infection are constantly being refined and improved, virus isolation in tissue culture is still the most definitive method of detecting HSV, and it is the most widely used. In this chapter detailed procedures for HSV isolation and typing are described, with brief reviews on methods that have been used in conjunction with virus isolation when cell culture facilities are not available.