Updated on: September 28, 2020

ICD-10 Coding Tips for Influenza

Original story posted on: September 20, 2020

The flu season is coming.

There has been much discussion about COVID-19 this year, but as autumn approaches, thoughts turn towards influenza season. The Advisory Committee on Immunization Policies (ACIP) recently published guidelines for flu vaccination. Their advice is that routine annual vaccination is recommended for everyone 6 months of age and older. The United States vaccines will include updates to influenza A (H1N1) pdm09, influenza A (H3N2), and influenza B (Victoria). There are two new vaccines for people 65 years old and older. They are Fluzone High-Dose Quadrivalent and Fluad Quadrivalent.

This year’s flu season will occur simultaneously with COVID-19. It is believed that the flu vaccine will reduce symptoms that may be confused with COVID-19. 

The Centers for Disease Control and Prevention (CDC) has updated their guidance for patients who have an egg allergy. Until recently, people with an egg allergy were advised not to get the flu vaccine. The new advice indicates that the flu vaccine could be administered to people with an egg allergy at a healthcare facility. The most recent guidance is that only patients with a severe allergic reaction to eggs are required to have the vaccination at a healthcare facility, if a vaccine other than ccIIV4 or RIV4 is given. It is important to disclose an egg allergy and its severity before getting the flu vaccination.

Vaccination is recommended before the end of October. Optimally, it is recommended to be vaccinated before influenza begins in your community. Manufacturers will provide 194-198 million doses of the flu vaccine. The vaccine is being distributed now.

The high-risk groups for influenza include:

  • Children 6 months up to 5 years old
  • All people 50 and older
  • People with chronic respiratory, cardiovascular, renal, hepatic, neurologic, hematologic, or metabolic disorders
  • Immunocompromised people
  • Pregnant women and those planning to be pregnant
  • Residents of nursing homes and long-term care facilities
  • American Indian natives
  • People with body mass index greater than or equal to 40
  • Children/adolescents receiving aspirin or salicylate containing medications

The ICD-10-CM coding for influenza begins with the main term of Influenza. It is important to designate novel or non-novel as a descriptor. In the table below is a listing of influenza codes:




Type A, non-novel


Influenza due to other identified influenza virus

Type A, H1N1


Influenza due to novel influenza A virus with other respiratory manifestations. 

Type B


Influenza due to other identified influenza virus

Type C


Influenza due to other identified influenza virus



Influenza due to other unidentified influenza virus with other respiratory manifestations

Unspecified with manifestations


Influenza due to other unidentified influenza virus

Novel influenza A is also known as bird or avian flu.

Other factors that may impact the influenza code are the manifestations, such as encephalopathy, enteritis, laryngitis, myocarditis, otitis media, pneumonia, etc. This information is captured in the fourth character. The more specific the reported data, the better the population health information.

The immunization is reported with Z23. The flu vaccination is important to report for quality scores as well. The National Healthcare Safety Network (NHSN) utilizes this information for reporting statistics. Facilities (such as ambulatory surgery centers, inpatient psychiatric facilities, and outpatient dialysis centers) that are not required to report the data may voluntarily report.

The CDC will provide weekly updates regarding the 2020-21 flu season. It is never too late to get vaccinated!

Laurie M. Johnson, MS, RHIA, FAHIMA AHIMA Approved ICD-10-CM/PCS Trainer

Laurie M. Johnson, MS, RHIA, FAHIMA, AHIMA Approved ICD-10-CM/PCS Trainer is currently a senior healthcare consultant for Revenue Cycle Solutions, based in Pittsburgh, Pa. Laurie is an American Health Information Management Association (AHIMA) approved ICD-10-CM/PCS trainer. She has more than 35 years of experience in health information management and specializes in coding and related functions. She has been a featured speaker in over 40 conferences. Laurie is a member of the ICD10monitor editorial board and makes frequent appearances on Talk Ten Tuesdays.