HHV-6 accounted for 5% of all herpetic viral encephalitis in immunocompetent Mexican patients

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Psychiatric disorders were the most common prodomal symptom (58%) and this was significantly different from patients with non-herpesvirus encephalitis.

Many different viruses, including herpesviruses, can cause encephalitis in immunocompromised and immunocompetent people. In the past decade, PCR of cerebrospinal fluid has become the gold standard for diagnosis of viral encephalitis.

Garcia et al. studied all Mexican patients seen over five years at the National Institute of Neurology and Neurosurgery of Mexico in whom herpesvirus encephalitis was suspected. The patients had multiple symptoms and signs including fever; meningeal syndrome; impaired consciousness; drowsiness; stupor; coma; seizures either partial or generalized; and  “psychiatric” disturbances such as aggression, agitation, hallucinations, delusions, impaired memory, and poor judgment. Of the 502 patients who met inclusion criteria for the study, and had PCR testing done of spinal fluid, 59 (12%) had PCR evidence of infection with one of the  herpesviruses. Among those 59 patients, the percentage positive for specific herpesviruses was:

Type of herpesvirus














Those with PCR-confirmed herpesvirus infection were more likely than those without confirmed infection to have had prodromal “psychiatric” disorders, as defined above, (P=0.002) and impairment of consciousness (p=0.0001). They were not more likely to be immunosuppressed. Overall mortality was 14% in this cohort.

 Individual clinical features of “encephalitis” had poor sensitivity and positive predictive value in identifying PCR-positive cases. However, combinations of multiple symptoms and signs were said to provide very high sensitivity, specificity and predictive values. 

The most important limitations of this study are two.  First, for reasons that are unclear, PCR diagnosis of other viral causes of encephalitis were not performed in these patients with suspected herpesvirus encephalitis, even though many non-herpesviruses can produce a clinical picture similar to herpesvirus encephalitis. Second, none of the PCR products were reportedly sequenced to confirm the “positive” results.

Read the full article: Garcia 2021