A 37 year old newly married man presents with multiple blister-like lesions on the glans of his penis, appearing over the past 2 days. On questioning, he recalls similar episodes over the past 2 years. Examination is remarkable for tender, 3-4 mm vesicular lesions on the shaft of his penis with no apparent crusting, drainage, or bleeding. There is also slight bilateral inguinal adenopathy. During the asymptomatic period between outbreaks, where would the causative agent likely have been found?

This is a classic example of an infection with herpes simplex virus (probably type 2). This agent causes lytic infections in mucoepithelial cells. It is then retrogradely transpoed into neurons of the sacral ganglia, where it lays dormant during the asymptomatic phase of the disease. Fibroblasts may be infected by cytomegalovirus, another herpes virus, but this produces a distinctive mononucleosis-like syndrome in most normal individuals. Lymphocytes and macrophages may be infected by herpes simplex type 2 but are not the site of residence of the virus during quiescent periods. Ref: Brooks G.F. (2013). Chapter 33. Herpesviruses. In G.F. Brooks (Ed), Jawetz, Melnick, & Adelberg's Medical Microbiology, 26e.