2026 ICD-10-CM Diagnosis Code A70Chlamydia psittaci infections

ICD-10-CM Codes›A00–B99›A70-A74›A70

ICD-10-CM A70
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

A70 is a billable ICD-10-CM diagnosis code for Chlamydia psittaci infections. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 865 through 866. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 1 closely related codes. Coders also document this condition as exanthem caused by Chlamydophila psittaci. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections.

Code Identity

ICD-10-CM Code
A70
Billable Status
Yes — Valid for Submission
Code Describes
Chlamydia psittaci infections
Short Description
Chlamydia psittaci infections
Same as the full description in the CMS dataset.
Chapter
A70-A74
Other diseases caused by chlamydiae

Code Classification

ChapterA00–B99Certain infectious and parasitic diseases
SectionA70-A74Other diseases caused by chlamydiae
CategoryA70Chlamydia psittaci infections
This CodeA70Chlamydia psittaci infections

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Exanthem caused by Chlamydophila psittaci
  • Ornithosis
  • Ornithosis with pneumonia
  • Pneumonia caused by Chlamydiaceae

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Ornithosis
  • Parrot fever
  • Psittacosis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INF003
Bacterial infections
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Ornithosis

    disease caused by the chlamydophila psittaci bacteria, usually transmitted from birds to humans.

Patient EducationClinical

Bacterial Infections

Bacteria are tiny organisms (living things) that have only one cell. Under a microscope, they look like balls, rods, or spirals. They can be found almost everywhere on Earth. There are lots of bacteria in and on your body. In fact, your body has about 10 times more bacteria cells than human cells.

The full article covers:

  • What are bacteria?
  • How do bacterial infections spread?
  • What are the treatments for bacterial infections?
  • Can bacterial infections be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert A70 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
073.9 Ornithosis NOS
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About A70Overview

What is the ICD-10 code for Chlamydia psittaci infections?

The ICD-10-CM code for Chlamydia psittaci infections is A70. It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is A70 (Chlamydia psittaci infections) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Chlamydia psittaci infections on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does A70 group to?

When Chlamydia psittaci infections is the principal diagnosis on an inpatient stay, it groups to MS-DRG 865, 866, with relative weights from 0.8696 to 1.4983 depending on complications. Higher weights mean higher Medicare reimbursement.

Is A70 a CC or MCC?

CMS lists A70 as a CC (complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 1 closely related codes in its exclusion list.

What is the ICD-9 equivalent of A70?

Under the General Equivalence Mappings, Chlamydia psittaci infections converts to ICD-9-CM 073.9 (ornithosis NOS). The mapping is approximate, so confirm the match fits the documentation.