Review of 3200 serially received CSF samples submitted for type-specific HSV detection by PCR in the reference laboratory setting.

Previously, studies of CNS infection have indicated substantially greater prevalence of HSV1 than HSV2. In reviewing unexpectedly high numbers of HSV2 infections among CSF specimens submitted to our laboratories for PCR testing, we discovered an age and gender bias suggesting a need to examine the demographics of those patients whose specimens tested positive for HSV. Some 3200 CSF specimens submitted for HSV testing were randomly selected for analysis. HSV1 was detected in 26 specimens (nine male, 17 female; average age 51 years) and HSV2 in 36 specimens (13 male, 23 female; average age 34 years). In general, there were almost twice as many HSV1 and HSV2 infections detected in females as in males. The entire group (22 male, 40 female) exhibited a preponderance of HSV2 over HSV1 infections (36:26). In contrast, the ratio of HSV2 to HSV1 infection was 3:13 in the over 60 age group of our study (11 of the 13 HSV1 infections in this age group occurred in females). In the subgroup of 21 patients aged 15-40 years (six male, 15 female), the ratio of HSV2 to HSV1 was 16:5. In the 15 infections in the group aged 41-60 years, the ratio of HSV2 to HSV1 was 12:4. In summary, our data indicate extraordinary differences in the relative frequency of HSV1 vs HSV2 CNS infections in teenagers, young adults (15-40 years), middle age (41-60) and in the elderly (>60 years), including a particular bias for HSV1 CNS infection in females over age 70 years.