A99 — Unspecified viral hemorrhagic fever
Is A99 billable?
Yes, but A99 is an unspecified code. A99 is a valid, billable ICD-10-CM code for encounters from October 1, 2026 through September 30, 2027. However, A99 is an unspecified or catch-all code. Payers apply additional scrutiny to unspecified codes and many deny them when the medical record supports a more specific option, so check the documentation before selecting A99.
A99 at a glance
| Code | A99 |
|---|---|
| Description | Unspecified viral hemorrhagic fever |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does A99 group to?
A99 sits in MDC 18 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 865Viral Illness with MCCmedical
- 866Viral Illness without MCCmedical
As a secondary diagnosis, A99 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is A99 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to A99. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Fever › hemorrhagicNOS › viral (inanition) (of unknown origin) (persistent) (with chills) (with rigor)
Use additional code — inherited from Chapter 1
Report an additional code alongside A99 to fully describe the condition. A99 is sequenced first.
- code to identify resistance to antimicrobial drugs (Z16.-)
Excludes2 — not included here — inherited from Chapter 1
The conditions below are not part of A99, but a patient may have both at the same time. When documentation supports it, A99 and the excluded code may both be reported.
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
How long has A99 existed?
A99 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.