| Virus family | Virus | Typical transmission route | Geographic distribution / epidemiology | Case fatality rate / severity notes |
|---|---|---|---|---|
| **Herpesviridae** | **HSV-1** | Reactivation or primary infection with neural spread to CNS; trans-synaptic spread from trigeminal/olfactory pathways | Worldwide; leading cause of sporadic, non-epidemic encephalitis in developed settings; HSV accounts for >90% of encephalitis cases among immunocompetent adults in HSV encephalitis series (pqac-00000001, pqac-00000006, pqac-00000012) | Untreated HSE mortality historically ~70%; with aciclovir, mortality falls to ~10–25%; long-term neurologic disability remains common (pqac-00000001) |
| **Herpesviridae** | **HSV-2** | Perinatal/neonatal transmission most important for encephalitic disease; less commonly adult CNS infection | Worldwide; causes ~80% of neonatal HSV CNS cases in cited review (pqac-00000006) | Specific CFR not consistently separated from HSV-1 in retrieved evidence; neonatal disease can be severe and life-threatening (pqac-00000006) |
| **Flaviviridae** | **Japanese encephalitis virus (JEV)** | Mosquito-borne | Endemic in Southeast Asia and the Western Pacific; most common epidemic viral encephalitis globally; ~68,000 cases annually, with ~1.15 billion people at risk (pqac-00000001, pqac-00000002) | Review evidence notes 10,000–15,000 deaths annually; severe neurologic sequelae common among survivors (pqac-00000002) |
| **Flaviviridae** | **West Nile virus (WNV)** | Mosquito-borne | Africa, Europe, Middle East, North America, West Asia; important cause of arboviral neuroinvasive disease, including in Europe (pqac-00000002, pqac-00000006) | In retrieved evidence, exact CFR for encephalitis not consistently quantified; recognized cause of severe neuroinvasive disease with substantial morbidity (pqac-00000002, pqac-00000006) |
| **Flaviviridae** | **Tick-borne encephalitis virus (TBEV)** | Ixodes tick bite; less often alimentary transmission via unpasteurized dairy | Focally endemic in Europe and Asia; ~5,000–10,000 human cases annually in endemic areas; highest incidence in older adults, male predominance (pqac-00000003) | Mortality varies by subtype; severe disease risk higher in age ≥60, immunocompromise, and Far Eastern subtype infection; often causes permanent neurologic/cognitive sequelae (pqac-00000003) |
| **Flaviviridae** | **Zika virus (ZIKV)** | Primarily mosquito-borne; also sexual, vertical, and transfusion routes recognized broadly | Tropics/subtropics with outbreaks in the Americas, Pacific, Asia, and Africa; included among major neurotropic RNA viruses causing VE (pqac-00000002, pqac-00000006) | Exact encephalitis CFR not established in retrieved evidence; neurologic disease recognized but encephalitis less common than congenital/CNS developmental complications (pqac-00000002) |
| **Flaviviridae** | **Dengue virus (DENV)** | Mosquito-borne | Global tropical/subtropical distribution; increasing autochthonous transmission in Europe noted in recent review (pqac-00000002) | Exact encephalitis CFR not given in retrieved evidence; dengue can be neuropathogenic and contribute to VE burden (pqac-00000002) |
| **Togaviridae / Alphavirus** | **Eastern equine encephalitis virus (EEEV)** | Mosquito-borne; laboratory aerosol exposure also documented | Primarily eastern North America; average ~11 annual human cases, but outbreaks occur (pqac-00000004) | High CFR ~30–75%; among survivors, 50–90% experience neurologic sequelae (pqac-00000004, pqac-00000005) |
| **Togaviridae / Alphavirus** | **Venezuelan equine encephalitis virus (VEEV)** | Mosquito-borne; aerosol exposure possible in laboratory/biothreat settings | Americas; causes epizootic and enzootic disease in humans and equids (pqac-00000005, pqac-00000007) | Overall mortality usually <1%, but can reach ~10% in adults with neurologic disease and ~35% in children in cited review (pqac-00000005) |
| **Togaviridae / Alphavirus** | **Western equine encephalitis virus (WEEV)** | Mosquito-borne | Historically Americas, especially western North America (pqac-00000005, pqac-00000007) | CFR ~3–15%; neurologic sequelae common in survivors (pqac-00000005) |
| **Rhabdoviridae** | **Rabies virus** | Animal bite with saliva inoculation; neuronal spread to CNS | Worldwide, especially Asia and Africa; classic neurotropic encephalitic virus included among major VE causes (pqac-00000002, pqac-00000006) | Once clinical encephalitis develops, rabies is typically nearly uniformly fatal; exact figure not quantified in retrieved evidence (pqac-00000002, pqac-00000006) |
| **Picornaviridae** | **Enteroviruses (e.g., EV71)** | Fecal-oral, respiratory, close contact | Worldwide, especially pediatric populations in Asia-Pacific outbreaks; important cause of viral CNS infection (pqac-00000002, pqac-00000006) | Exact CFR for encephalitis not consistently reported in retrieved evidence; can cause severe pediatric brainstem encephalitis and neurologic complications (pqac-00000006) |
| **Coronaviridae** | **SARS-CoV-2** | Respiratory transmission | Worldwide pandemic distribution; included among major RNA viruses associated with VE and post-infectious CNS syndromes (pqac-00000002, pqac-00000011) | Exact CFR for encephalitis not established in retrieved evidence; neurologic involvement recognized but heterogeneous (pqac-00000002, pqac-00000011) |
| **Paramyxoviridae** | **Measles virus** | Respiratory droplets / airborne | Worldwide where vaccination gaps persist; included among viral encephalitis pathogens and also relevant to post-vaccine susceptibility syndromes in interferon-pathway deficiencies (pqac-00000002, pqac-00000000) | Exact encephalitis CFR not quantified in retrieved evidence; measles encephalitis can be severe/fatal (pqac-00000002) |
| **Orthomyxoviridae / Pneumoviridae and others** | **Respiratory viruses with encephalitic complications (e.g., RSV, influenza)** | Respiratory transmission | Worldwide; RSV meta-analysis found encephalitis/encephalopathy is uncommon but notable across adults and children (pqac-00000002) | RSV-associated encephalitis/encephalopathy pooled prevalence ~2.20 per 100 RSV cases; case fatality 0.43% in observational studies and 10.71% in case reports, reflecting publication bias (pqac-00000002) |


*Table: This table summarizes the principal viral causes of viral encephalitis by virus family, with transmission route, geographic distribution, and severity or case-fatality information based on the gathered evidence. It is useful for comparing the epidemiologic patterns and relative clinical severity of major encephalitic viruses.*