A01.05
BillableTyphoid osteomyelitis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A01.05 an HCC code?
Yes. A01.05 maps to Bone/Joint/Muscle Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for A01.05
For A01.05 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed A01.05 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
A01.05 is the ICD-10-CM diagnosis code for typhoid osteomyelitis. This is a serious bone infection caused by typhoid fever bacteria that has spread to the bone tissue. It represents a complication of untreated or severe typhoid infection where the bacteria invade and inflame the bone marrow and surrounding bone structure. A01.05 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering intestinal infectious diseases (a00-a09).
Under the CMS-HCC V28 risk adjustment model, A01.05 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.209. Under the older V24 model, A01.05 mapped to the same category but with a base RAF weight of 0.482 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This code should only be used when typhoid fever has progressed to cause osteomyelitis; do not use if only typhoid fever is present without bone involvement. Because A01.05 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A01.05 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code should only be used when typhoid fever has progressed to cause osteomyelitis; do not use if only typhoid fever is present without bone involvement
- •Ensure documentation clearly indicates both the typhoid infection and the osteomyelitis complication; this is a manifestation code that requires the underlying typhoid condition to be documented
Clinical Significance
Typhoid osteomyelitis is a rare, serious complication where Salmonella typhi infects bone tissue, often affecting long bones or vertebrae. It requires prolonged antibiotic therapy (often 6-8 weeks) and may necessitate surgical debridement, representing significant disease burden and resource utilization.
Documentation Requirements
- ✓Confirmed Salmonella typhi infection with documented bone involvement
- ✓Imaging evidence of osteomyelitis (MRI preferred, or bone scan/CT showing osseous changes)
- ✓Specific bone(s) or anatomic site(s) affected
- ✓Bone biopsy or culture results if performed, identifying Salmonella typhi
- ✓Duration of infection (acute vs. chronic) and treatment plan documenting prolonged antibiotic course