| A80 | Acute poliomyelitis |
| A80.0 | Acute paralytic poliomyelitis, vaccine-associated |
| A80.1 | Acute paralytic poliomyelitis, wild virus, imported |
| A80.2 | Acute paralytic poliomyelitis, wild virus, indigenous |
| A80.3 | Acute paralytic poliomyelitis, other and unspecified |
| A80.30 | Acute paralytic poliomyelitis, unspecified |
| A80.39 | Other acute paralytic poliomyelitis |
| A80.4 | Acute nonparalytic poliomyelitis |
| A80.9 | Acute poliomyelitis, unspecified |
| A81 | Atypical virus infections of central nervous system |
| A81.0 | Creutzfeldt-Jakob disease |
| A81.00 | Creutzfeldt-Jakob disease, unspecified |
| A81.01 | Variant Creutzfeldt-Jakob disease |
| A81.09 | Other Creutzfeldt-Jakob disease |
| A81.1 | Subacute sclerosing panencephalitis |
| A81.2 | Progressive multifocal leukoencephalopathy |
| A81.8 | Other atypical virus infections of central nervous system |
| A81.81 | Kuru |
| A81.82 | Gerstmann-Sträussler-Scheinker syndrome |
| A81.83 | Fatal familial insomnia |
| A81.89 | Other atypical virus infections of central nervous system |
| A81.9 | Atypical virus infection of central nervous system, unspecified |
| A82 | Rabies |
| A82.0 | Sylvatic rabies |
| A82.1 | Urban rabies |
| A82.9 | Rabies, unspecified |
| A83 | Mosquito-borne viral encephalitis |
| A83.0 | Japanese encephalitis |
| A83.1 | Western equine encephalitis |
| A83.2 | Eastern equine encephalitis |
| A83.3 | St Louis encephalitis |
| A83.4 | Australian encephalitis |
| A83.5 | California encephalitis |
| A83.6 | Rocio virus disease |
| A83.8 | Other mosquito-borne viral encephalitis |
| A83.9 | Mosquito-borne viral encephalitis, unspecified |
| A84 | Tick-borne viral encephalitis |
| A84.0 | Far Eastern tick-borne encephalitis [Russian spring-summer encephalitis] |
| A84.1 | Central European tick-borne encephalitis |
| A84.8 | Other tick-borne viral encephalitis |
| A84.9 | Tick-borne viral encephalitis, unspecified |
| A85 | Other viral encephalitis, not elsewhere classified |
| A85.0 | Enteroviral encephalitis |
| A85.1 | Adenoviral encephalitis |
| A85.2 | Arthropod-borne viral encephalitis, unspecified |
| A85.8 | Other specified viral encephalitis |
| A86 | Unspecified viral encephalitis |
| A87 | Viral meningitis |
| A87.0 | Enteroviral meningitis |
| A87.1 | Adenoviral meningitis |
| A87.2 | Lymphocytic choriomeningitis |
| A87.8 | Other viral meningitis |
| A87.9 | Viral meningitis, unspecified |
| A88 | Other viral infections of central nervous system, not elsewhere classified |
| A88.0 | Enteroviral exanthematous fever [Boston exanthem] |
| A88.1 | Epidemic vertigo |
| A88.8 | Other specified viral infections of central nervous system |
| A89 | Unspecified viral infection of central nervous system |