ICD-10 Code for Meningoencephalitis
The ICD-10-CM code for meningoencephalitis is G04.90 — Encephalitis and encephalomyelitis, unspecified. This is the code the Alphabetic Index gives for meningoencephalitis with no further qualifier, valid for FY2027 (October 1, 2026 – September 30, 2027).
G04.90 is billable but unspecified. If the documentation names a type, site or cause, one of the more specific codes below is likely expected.
Which meningoencephalitis code should you use?
The Alphabetic Index lists 25 codes under Meningoencephalitis. Which one applies depends on the qualifier documented in the record — the type, site, cause, or associated condition. Find the qualifier below, then verify the code in the Tabular List before using it.
By type
| acute NEC | A86 | Unspecified viral encephalitis | |
| bacterial NEC | G04.2 | Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified | |
| California | A83.5 | California encephalitis | |
| diphasic | A84.1 | Central European tick-borne encephalitis | |
| eosinophilic | B83.2 | Angiostrongyliasis due to Parastrongylus cantonensis | |
| epidemic | A39.81 | Meningococcal encephalitis | |
| herpesviral, herpetic | B00.4 | Herpesviral encephalitis | |
| infectious | A86 | Unspecified viral encephalitis | |
| influenzal | G00.0 | Hemophilus meningitis | |
| Listeria monocytogenes | A32.12 | Listerial meningoencephalitis | |
| lymphocytic | A87.2 | Lymphocytic choriomeningitis | |
| mumps | B26.2 | Mumps encephalitis | |
| parasitic NEC | B89 | Unspecified parasitic disease | |
| pneumococcal | G04.2 | Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified | |
| primary amebic | B60.2 | Naegleriasis | |
| specific | A52.14 | Late syphilitic encephalitis | |
| specified organism NEC | G04.81 | Other encephalitis and encephalomyelitis | |
| staphylococcal | G04.2 | Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified | |
| streptococcal | G04.2 | Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified | |
| syphilitic | A52.14 | Late syphilitic encephalitis | |
| toxic NEC | G92.8 | Other toxic encephalopathy | |
| tuberculous | A17.82 | Tuberculous meningoencephalitis | |
| virus NEC | A86 | Unspecified viral encephalitis |
Meningoencephalitis herpesviral, herpetic
Meningoencephalitis in
| blastomycosis NEC | B40.81 | Blastomycotic meningoencephalitis | |
| diseases classified elsewhere | G05.3 | Encephalitis and encephalomyelitis in diseases classified elsewhere | |
| free-living amebae | B60.2 | Naegleriasis | |
| Hemophilus influenzae | G00.0 | Hemophilus meningitis | |
| herpes | B00.4 | Herpesviral encephalitis | |
| H. influenzae | G00.0 | Hemophilus meningitis | |
| Lyme disease | A69.22 | Other neurologic disorders in Lyme disease | |
| mumps | B26.2 | Mumps encephalitis | |
| Naegleria | B60.2 | Naegleriasis | |
| Parastrongylus cantonensis | B83.2 | Angiostrongyliasis due to Parastrongylus cantonensis | |
| toxoplasmosis | B58.2 | Toxoplasma meningoencephalitis | |
| herpes › due to herpesvirus 6 | B10.01 | Human herpesvirus 6 encephalitis | |
| herpes › due to herpesvirus 7 | B10.09 | Other human herpesvirus encephalitis | |
| herpes › specified NEC | B10.09 | Other human herpesvirus encephalitis | |
| toxoplasmosis › congenital | P37.1 | Congenital toxoplasmosis |
Index terms and codes are reproduced from the official ICD-10-CM FY2027 release. The Alphabetic Index is a finding aid — a code must always be verified in the Tabular List before it is reported. Data sources