I-10 Corner: Chapter 1 - Certain Infectious and Parasitic Disease

on Tuesday, 08 October 2013. All News Items | Documentation | Coding

This month MMP will focus on some of the important changes and guidelines covering Chapter One “Certain Infectious and Parasitic Diseases”.

Chapter 1 is divided into 22 separate blocks covering two alpha characters A00-B99 and includes:

  • Diseases generally recognized as communicable or transmissible as well as a few diseases of unknown but possibly infectious origin.

Type I Excludes:

  • Certain localized infections – refer to body system related chapters.
  • Influenza and other acute respiratory infections (J00-J22)

Type 2 Excludes:

  • Carrier or suspected carrier of infectious disease (Z22.-)

A separate subchapter was created for “Infections with a Predominantly Sexual Mode of Transmission” (A50-A64) to appropriately group these type diseases together:

  • Human Immunodeficiency Virus (HIV) is excluded in this range of codes.

For cases with infections shown to have an associated drug resistance, code Z16 should be assigned in addition to the infection code to show the associated drug resistance.                      

  • Coding Guideline I.C 1.c. – Infections Resistant to Antibiotics:  Many bacterial infections are resistant to current antibiotics. It is necessary to identify all infections documented as antibiotic resistant.

Streptococcal Sore Throat has been relocated from Chapter 1 to Chapter 10 – Diseases of the Respiratory System.

Tuberculosis (TB):  

  • ICD-10-CM will not ask for information denoting how the disease was identified.
  • The codes for Tuberculosis have been restructured and consolidated. Assignment is now based on anatomical site or type.

Intestinal Infections:

  • Codes will now identify type of infection.
    • Viral
    • Bacterial
    • Fungal or parasitic/amebic
    • Options available for “Other “ and “Unspecified”

Categories B95.0-B99.9 are supplementary codes to identify the infectious agent(s) in diseases classified elsewhere in which there is no organism identified as part of the infection code.

  • Refer to Coding Guideline I.C.1.b.

Human Immunodeficiency Virus (HIV) Infections

HIV is the virus that can lead to AIDS (Acquired Immunodeficiency Syndrome).   People with this illness are much more vulnerable to infections due to the attack and alteration to their immune system. This is prone to get worse as the disease progresses. The human body is not capable of fighting off this virus. Once a person is infected with HIV, it is an affliction for the rest of their life.

HIV is found in the body fluids of an infected person and can be transmitted:

  • From one person to another through blood-to-blood and/or sexual contact.
  • Newborn infants can acquire HIV:
    • During pregnancy
    • Through delivery
    • Through breast feeding
  • Blood transfusion
  • Sharing hypodermic needles

There is a subcategory and four codes to classify the HIV virus in ICD-10-CM.

B20 - Human Immunodeficiency Virus (HIV) disease

Assign code B20 as the principal diagnosis when a patient is admitted with an HIV-related condition. An additional diagnosis code should be used to identify all reported manifestations of HIV infection.

  • Refer to Coding Guideline I.C.1.a.2.a.
  • Code only confirmed cases of HIV infection.
  • Confirmation does not require a positive serology or culture for HIV. The physician’s diagnostic statement is sufficient.
    • Refer to Coding Guideline I.C. 1.a.1.
  • People with HIV can acquire many infections that are called “Opportunistic Infections” or OIs.


  • Acquired Immune Deficiency Syndrome (AIDS)
  • AIDS-related Complex (ARC)
  • HIV Infection, Symptomatic

Excludes Type 1:

  • Asymptomatic Human Immunodeficiency Virus (HIV) Infection Status (Z21)
  • Exposure to HIV virus (Z20.6)
  • Inconclusive Serologic Evidence of HIV (R75)

Z21 - Asymptomatic Human Immunodeficiency Virus (HIV) Infection Status

Code Z21 is used for reporting a patient diagnosed with a positive HIV status but has never been diagnosed with any type of manifestation or OI.

  • Includes HIV positive NOS
  • Once a patient has developed an HIV-related OI, the patient should always be assigned code B20 for any future admission/encounter.
    • Code Z21 should never be assigned again for a patient diagnosed with HIV/AIDS even if there is no infection or HIV related condition during that present admission.
  • Codes B20 and Z21 should never be assigned together during the same admission.

R75 - Inconclusive laboratory evidence of Human Immunodeficiency Virus (HIV)

  • An inconclusive serology test, but no definitive diagnosis or manifestation of the HIV infection.

Z20.6 - Exposure to HIV Virus

This code is assigned only when a patient has been exposed or may have come in contact with the HIV virus.

Some Common HIV Infections:   (this list is not all or inclusive)

  • Pneumocystis pneumonia (PCP) - Serious infection which causes inflammation and fluid buildup in the lungs.
  • Cytomegalovirus - An opportunistic infection whichtakes advantage of a patient’s weakened immune system.
  • Tuberculosis (TB) - Leading cause of death for people infected with HIV.
  • Mycobacterium Avium Complex (MAC) - Usually happens only after a patient has been diagnosed with AIDS and when their CD4 cell counts drop below 50.
  • Dementia - AIDS dementia is caused by the HIV virus itself, not by the opportunistic infections.
  • AIDS Wasting Syndrome - Occurs when a patient with AIDS has lost at least 10% of their body weight -- especially muscle. The patient could experience at least 30 days of diarrhea, extreme weakness and fever that's not related to an infection.
  • Non-Hodgkin’s Lymphoma - As a result ofa weakened immune system, a patient is prone to develop certain cancers.
  • Lipodystrophy - Also known as “fat redistribution”.   This is when the body has problems in the way it produces, uses, and stores fat.
  • Kaposi’s Sarcoma (KS) - Type of cancer affecting mainly the skin, mouth, and lymph nodes (infection-fighting glands). Other organs such as the lungs and gastrointestinal tract can be affected as well.

A list of Meds currently available in the US

Epivir (lamivudine, "3TC") Fortovase (saquinavir)
Fuzeon (enfuvirtide) Hivid (zalcitabine, "ddC")
Invirase (saquinavir) Kaletra (lopinavir)
Lexiva (fosamprenavir) Norvir (ritonavir)
Rescriptor (delavirdine) Retrovir (zidovudine, "AZT")
Reyataz (atazanavir) Stribild (Emtriva + Viread + elvitegravir)
Sustiva (efavirenz) Trizivir (AZT/3TC/abacavir)
Truvada (Emtriva + Viread) Videx (didanosine, "ddI")
Viracept (nelfinavir) Viramune (nevirapine)
Viread (tenofovir) Zerit (stavudine, "d4T")
Ziagen (abacavir)

Note: When coding the HIV Disease and Sepsis, it is very important to read and familiarize yourself with the Coding Guidelines.


Article by Marsha Manning

Marsha Manning RHIT, CCS, AHIMA Approved ICD-10-CM/PCS Trainer, is an Inpatient Coding Consultant at Medical Management Plus, Inc.  Marsha has over 23 years experience in the coding profession and has held various positions such as DRG coordinator, Coding Supervisor and HIM Supervisor. In her current position, Marsha reviews records and assists clients with coding accuracy, compliance, education and Case Mix Index (CMI) as they relate to specific entities concerning Medicare. You may contact Marsha at This email address is being protected from spambots. You need JavaScript enabled to view it.This email address is being protected from spambots. You need JavaScript enabled to view it..

This material was compiled to share information. MMP, Inc. is not offering legal advice. Every reasonable effort has been taken to ensure the information is accurate and useful.

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