Version October 2024
| Etiology | Relative frequency of meningitis versus encephalitis | Potential clinical clues |
| Enteroviruses | ||
| Coxsackie A and B viruses Echoviruses Numbered enteroviruses (eg, A71) | Meningitis > Encephalitis | Rash, herpangina, hand-foot-mouth disease, conjunctivitis, pharyngitis, pleurodynia, myopericarditis |
| Polioviruses | Meningitis > Encephalitis | Flaccid paralysis |
| Parechoviruses | ||
| Parechovirus type 3 | Meningitis > Encephalitis | Palmar and plantar rash; sepsis-like illness in young infants |
| Arthropod-borne viruses (arboviruses) | ||
| West Nile virus | Encephalitis > Meningitis | Rash; mosquito exposure |
| St. Louis encephalitis virus | Encephalitis = Meningitis | Mosquito exposure |
| La Crosse (California) encephalitis virus | Encephalitis > Meningitis | Mosquito exposure |
| Eastern equine encephalitis virus | Encephalitis > Meningitis | Mosquito exposure |
| Western equine encephalitis virus | Encephalitis = Meningitis | Mosquito exposure |
| Powassan virus | Encephalitis > Meningitis | Tick exposure |
| Herpesviruses | ||
| Herpes simplex type 1 | Encephalitis > Meningitis | Oral lesions |
| Herpes simplex type 2 | Meningitis > Encephalitis | Genital lesions, sacral radiculopathy (urinary retention, constipation, paresthesia, weakness) |
| Cytomegalovirus | Encephalitis > Meningitis | Preterm neonate; immunocompromised host |
| Varicella zoster virus | Meningitis > Encephalitis | Vesicular rash; shingles (rash may not be present in some cases of viral reactivation) |
| Epstein-Barr virus | Encephalitis > Meningitis | Preceding signs of infectious mononucleosis – Malaise, headache, fever, pharyngitis, cervical lymph node enlargement |
| Other viruses | ||
| HIV (ie, acute retroviral syndrome) | Encephalitis = Meningitis | Intravenous drug use, high-risk sexual behavior |
| Influenza virus | Encephalitis > Meningitis | Classic influenza symptoms – Fever, cough, vomiting, headache, diarrhea |
| Lymphocytic choriomeningitis virus | Meningitis > Encephalitis | Rodent pets or contact with rodent droppings or urine |
| Measles virus | Encephalitis > Meningitis | Cough, coryza, conjunctivitis; occurs in unvaccinated or incompletely vaccinated individuals |
| Mumps virus | Meningitis > Encephalitis | Painful parotitis; occurs in unvaccinated or incompletely vaccinated individuals |
| Rabies virus | Encephalitis > Meningitis | Animal exposure; prodrome of nonspecific symptoms (fever, headache, malaise, myalgia, cough, sore throat, nausea, vomiting) |
| SARS-CoV-2 | Encephalitis = Meningitis | Preceding signs of COVID-19 – Fever, cough, respiratory symptoms |
| Zika virus | Encephalitis > Meningitis | Mosquito exposure; residence in or travel to an endemic region |
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