From the Guidelines
Patients with suspected viral meningitis or encephalitis should be tested for herpes simplex virus (HSV) types 1 and 2, enterovirus, and varicella-zoster virus (VZV) by PCR, as recommended by the most recent and highest quality study 1. The diagnostic approach typically involves PCR testing of cerebrospinal fluid obtained via lumbar puncture.
- HSV PCR testing of cerebrospinal fluid is particularly crucial as HSV encephalitis requires prompt treatment with acyclovir.
- Additional viruses to consider include cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), and mumps virus, although testing for these should be guided by additional features in the history and examination, such as immune compromise and travel history 1.
- For immunocompromised patients, additional testing for JC virus, HIV, and lymphocytic choriomeningitis virus may be warranted. The importance of early identification of the causative virus cannot be overstated, as specific antiviral treatments exist for some viral causes (particularly herpesviruses), while others require supportive care only 1.
- The use of PCR for amplification of microbial nucleic acids has greatly increased the ability to diagnose infections of the CNS, especially viral infections that are caused by herpesviruses and enteroviruses 1.
- A negative PCR result cannot be used as definitive evidence against the diagnosis, and clinical correlation is essential 1.
From the Research
Viruses to be Checked for in Suspected Viral Meningitis or Encephalitis
The following viruses should be considered for testing in patients with suspected viral meningitis or encephalitis:
- Enteroviruses, which are a common cause of aseptic meningitis and encephalitis in adults 2, 3, 4, 5
- Herpes simplex virus (HSV), including both HSV-1 and HSV-2, which can cause meningitis and encephalitis 3, 6, 4, 5
- Varicella-zoster virus (VZV), which can cause meningitis and encephalitis, particularly in individuals with a history of herpes zoster infection 3, 6, 4, 5
- Other viruses, such as arboviruses and LCM virus, which can also cause viral meningitis and encephalitis, although they are less common 3
Diagnostic Approaches
Diagnostic testing for these viruses can include:
- Polymerase chain reaction (PCR) of cerebrospinal fluid (CSF) samples to detect viral DNA or RNA 2, 6, 4, 5
- Serologic testing to detect antibodies against specific viruses 3, 6
- Virus isolation from CSF, stool, or throat samples 3
Considerations for Testing
When testing for these viruses, it is essential to consider the following:
- The timing of sample collection, as the diagnostic yield of PCR may be lower for CSF specimens obtained more than 2 days after clinical onset 2
- The use of multiplex PCR assays, which can detect multiple viruses simultaneously and improve diagnostic sensitivity 4
- The importance of interpreting test results in the context of clinical presentation and epidemiological factors 3, 5