2027 ICD-10-CM Diagnosis Code A70Chlamydia psittaci infections

ICD-10-CM Codes›A00–B99›A70-A74›A70

ICD-10-CM A70
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

A70 is a billable ICD-10-CM diagnosis code for Chlamydia psittaci infections. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) 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 Chlamydia 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 Chlamydia psittaci
  • Infection of skin caused by Chlamydia
  • Ornithosis
  • Ornithosis with pneumonia
  • Pneumonia caused by Chlamydiaceae

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to A70: its own notes plus those printed at block A70-A74 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • diseases generally recognized as communicable or transmissible

Applicable To

Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.

  • Ornithosis
  • Parrot fever
  • Psittacosis

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block A70-A74 Other diseases caused by chlamydiae applies to 8 codes
  • sexually transmitted chlamydial diseases (A55-A56)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • 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)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Chapter 1 (A00-B99) Certain infectious and parasitic diseases applies to 1,068 codes
  • code to identify resistance to antimicrobial drugs (Z16.-)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name A70, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming A70: they are not reported together with it, unless the two conditions are unrelated.

  • J16 Pneumonia due to other infectious organisms, not elsewhere classified
    ornithosis (A70)

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

  • Psittacosis

    infection with chlamydophila psittaci (formerly chlamydia psittaci), transmitted to humans by inhalation of dust-borne contaminated nasal secretions or excreta of infected birds. this infection results in a febrile illness characterized by pneumonitis and systemic manifestations.

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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

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, 2026 through September 30, 2027.

What MS-DRG does A70 group to?

When Chlamydia psittaci infections is the principal diagnosis on an inpatient stay, it groups to MS-DRG 866, 865, with relative weights from 0.8691 to 1.3153 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 2027. 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.