ICD-10-CM Code B27.9

Infectious mononucleosis, unspecified

Version 2020 Non-Billable Code

Not Valid for Submission

B27.9 is a "header" nonspecific and non-billable code code, consider using a code with a higher level of specificity for a diagnosis of infectious mononucleosis, unspecified. The code is NOT valid for the year 2020 for the submission of HIPAA-covered transactions.

ICD-10:B27.9
Short Description:Infectious mononucleosis, unspecified
Long Description:Infectious mononucleosis, unspecified

Consider the following ICD-10 codes with a higher level of specificity:

  • B27.90 - Infectious mononucleosis, unspecified without complication
  • B27.91 - Infectious mononucleosis, unspecified with polyneuropathy
  • B27.92 - Infectious mononucleosis, unspecified with meningitis
  • B27.99 - Infectious mononucleosis, unspecified with other complication

Clinical Information

  • HERPESVIRUS 4 HUMAN-. the type species of lymphocryptovirus subfamily gammaherpesvirinae infecting b cells in humans. it is thought to be the causative agent of infectious mononucleosis and is strongly associated with oral hairy leukoplakia leukoplakia hairy; burkitt lymphoma; and other malignancies.
  • INFECTIOUS MONONUCLEOSIS-. a common acute infection usually caused by the epstein barr virus herpesvirus 4 human. there is an increase in mononuclear white blood cells and other atypical lymphocytes generalized lymphadenopathy splenomegaly and occasionally hepatomegaly with hepatitis.
  • FATIGUE SYNDROME CHRONIC-. a syndrome characterized by persistent or recurrent fatigue diffuse musculoskeletal pain sleep disturbances and subjective cognitive impairment of 6 months duration or longer. symptoms are not caused by ongoing exertion; are not relieved by rest; and result in a substantial reduction of previous levels of occupational educational social or personal activities. minor alterations of immune neuroendocrine and autonomic function may be associated with this syndrome. there is also considerable overlap between this condition and fibromyalgia. from semin neurol 1998;182:237 42; ann intern med 1994 dec 15;12112: 953 9

Code Classification

  • Certain infectious and parasitic diseases (A00–B99)
    • Other viral diseases (B25-B34)
      • Infectious mononucleosis (B27)

Code History

  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016
    (First year ICD-10-CM implemented into the HIPAA code set)
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

Information for Patients


Infectious Mononucleosis

Infectious mononucleosis, or "mono", is an infection usually caused by the Epstein-Barr virus. The virus spreads through saliva, which is why it's sometimes called "kissing disease." Mono occurs most often in teens and young adults. However, you can get it at any age. Symptoms of mono include

  • Fever
  • Sore throat
  • Swollen lymph glands

Sometimes you may also have a swollen spleen. Serious problems are rare.

A blood test can show if you have mono. Most people get better in two to four weeks. However, you may feel tired for a few months afterward. Treatment focuses on helping symptoms and includes medicines for pain and fever, warm salt water gargles and plenty of rest and fluids.


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