| A81 | Atypical virus infections of central nervous system | NON-BILLABLE CODE |
| A81.0 | Creutzfeldt-Jakob disease | NON-BILLABLE CODE |
| A81.00 | Creutzfeldt-Jakob disease, unspecified | BILLABLE CODE |
| A81.01 | Variant Creutzfeldt-Jakob disease | BILLABLE CODE |
| A81.1 | Subacute sclerosing panencephalitis | BILLABLE CODE |
| A81.2 | Progressive multifocal leukoencephalopathy | BILLABLE CODE |
| A81.8 | Other atypical virus infections of central nervous system | NON-BILLABLE CODE |
| A81.81 | Kuru | BILLABLE CODE |
| A81.82 | Gerstmann-Straussler-Scheinker syndrome | BILLABLE CODE |
| A81.83 | Fatal familial insomnia | BILLABLE CODE |
| A81.89 | Other atypical virus infections of central nervous system | BILLABLE CODE |
| A81.9 | Atypical virus infection of central nervous system, unspecified | BILLABLE CODE |
