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  3. Diagnosis Codes in MS-DRG 866 - Viral Illness Without MCC

Diagnosis Codes in MS-DRG 866 - Viral Illness Without MCC

The Medicare Severity Diagnosis-Related Group (MS-DRG) is a patient classification system used to categorize hospital cases based on clinical similarity and expected resource use. MS-DRGs organize all possible principal diagnoses into mutually exclusive groups known as Major Diagnostic Categories (MDCs), which help determine reimbursement under the Medicare Inpatient Prospective Payment System.

This section lists the diagnosis codes included in MS-DRG V42.0: Viral Illness without MCC from October 1, 2024, through September 30, 2025.

MS-DRG: 866

MS-DRG Title: Viral Illness without MCC

MCD: 18

Relative Weight: 0.8847 Relative Weight
The relative weight of a diagnostic related group determines the reimbursement rate based on the severity of a patient's illness and the associated cost of care during hospitalization.

Geometric LOS: 0.88 Geometric Length of Stay
The geometric mean length of stay (GMLOS) is used by Medicare to calculate the reimbursement for patients whose medical treatment takes a much longer or shorter time than average.

Arithmetic LOS: 2.70 Arithmetic Length of Stay
The average length of stay (ALOS) reflects the average number of days a patient spends in a hospital for each admission.

  1. A74 - Other diseases caused by chlamydiae
  2. A74.8 - Other chlamydial diseases
  3. A80 - Acute poliomyelitis
  4. A92 - Other mosquito-borne viral fevers
  5. A92.3 - West Nile virus infection
  6. A93 - Other arthropod-borne viral fevers, not elsewhere clas
  7. A95 - Yellow fever
  8. A96 - Arenaviral hemorrhagic fever
  9. A98 - Other viral hemorrhagic fevers, not elsewhere classifi
  10. B00.8 - Other forms of herpesviral infections
  11. B01 - Varicella [chickenpox]
  12. B01.8 - Varicella with other complications
  13. B02 - Zoster [herpes zoster]
  14. B05 - Measles
  15. B05.8 - Measles with other complications
  16. B06 - Rubella [German measles]
  17. B06.8 - Rubella with other complications
  18. B08 - Other viral infections characterized by skin and mucou
  19. B08.0 - Other orthopoxvirus infections
  20. B08.01 - Cowpox and vaccinia not from vaccine
  21. B08.2 - Exanthema subitum [sixth disease]
  22. B08.6 - Parapoxvirus infections
  23. B08.7 - Yatapoxvirus infections
  24. B25 - Cytomegaloviral disease
  25. B26 - Mumps
  26. B26.8 - Mumps with other complications
  27. B27.0 - Gammaherpesviral mononucleosis
  28. B27.1 - Cytomegaloviral mononucleosis
  29. B27.8 - Other infectious mononucleosis
  30. B27.9 - Infectious mononucleosis, unspecified
  31. B33 - Other viral diseases, not elsewhere classified
  32. B34 - Viral infection of unspecified site
  33. B97 - Viral agents as the cause of diseases classified elsew
  34. B97.1 - Enterovirus as the cause of diseases classified else
  35. B97.2 - Coronavirus as the cause of diseases classified else
  36. B97.3 - Retrovirus as the cause of diseases classified elsew
  37. B97.8 - Other viral agents as the cause of diseases classifi
  38. J09.X - Influenza due to identified novel influenza A virus
  39. J10 - Influenza due to other identified influenza virus
  40. J10.8 - Influenza due to other identified influenza virus wi
  41. J11 - Influenza due to unidentified influenza virus
  42. J11.8 - Influenza due to unidentified influenza virus with o
  43. L44 - Other papulosquamous disorders
  44. T88.1 - Other complications following immunization, not else

  • -

    • A70 - Chlamydia psittaci infections

    • A90 - Dengue fever [classical dengue]

    • A91 - Dengue hemorrhagic fever

    • A94 - Unspecified arthropod-borne viral fever

    • A99 - Unspecified viral hemorrhagic fever

    • B03 - Smallpox

    • B04 - Monkeypox

    • B09 - Unspecified viral infection characterized by skin and mucous membrane lesions

    • Z21 - Asymptomatic human immunodeficiency virus [HIV] infection status

  • A74 - Other diseases caused by chlamydiae

    • A74.9 - Chlamydial infection, unspecified

  • A74.8 - Other chlamydial diseases

    • A74.81 - Chlamydial peritonitis

    • A74.89 - Other chlamydial diseases

  • A80 - Acute poliomyelitis

    • A80.4 - Acute nonparalytic poliomyelitis

  • A92 - Other mosquito-borne viral fevers

    • A92.0 - Chikungunya virus disease

    • A92.1 - O'nyong-nyong fever

    • A92.4 - Rift Valley fever

    • A92.5 - Zika virus disease

    • A92.8 - Other specified mosquito-borne viral fevers

    • A92.9 - Mosquito-borne viral fever, unspecified

  • A92.3 - West Nile virus infection

    • A92.30 - West Nile virus infection, unspecified

    • A92.31 - West Nile virus infection with encephalitis

    • A92.32 - West Nile virus infection with other neurologic manifestation

    • A92.39 - West Nile virus infection with other complications

  • A93 - Other arthropod-borne viral fevers, not elsewhere classified

    • A93.0 - Oropouche virus disease

    • A93.1 - Sandfly fever

    • A93.2 - Colorado tick fever

    • A93.8 - Other specified arthropod-borne viral fevers

  • A95 - Yellow fever

    • A95.0 - Sylvatic yellow fever

    • A95.1 - Urban yellow fever

    • A95.9 - Yellow fever, unspecified

  • A96 - Arenaviral hemorrhagic fever

    • A96.0 - Junin hemorrhagic fever

    • A96.1 - Machupo hemorrhagic fever

    • A96.2 - Lassa fever

    • A96.8 - Other arenaviral hemorrhagic fevers

    • A96.9 - Arenaviral hemorrhagic fever, unspecified

  • A98 - Other viral hemorrhagic fevers, not elsewhere classified

    • A98.0 - Crimean-Congo hemorrhagic fever

    • A98.1 - Omsk hemorrhagic fever

    • A98.2 - Kyasanur Forest disease

    • A98.3 - Marburg virus disease

    • A98.4 - Ebola virus disease

    • A98.8 - Other specified viral hemorrhagic fevers

  • B00.8 - Other forms of herpesviral infections

    • B00.89 - Other herpesviral infection

  • B01 - Varicella [chickenpox]

    • B01.0 - Varicella meningitis

    • B01.9 - Varicella without complication

  • B01.8 - Varicella with other complications

    • B01.81 - Varicella keratitis

    • B01.89 - Other varicella complications

  • B02 - Zoster [herpes zoster]

    • B02.7 - Disseminated zoster

    • B02.8 - Zoster with other complications

  • B05 - Measles

    • B05.1 - Measles complicated by meningitis

    • B05.4 - Measles with intestinal complications

    • B05.9 - Measles without complication

  • B05.8 - Measles with other complications

    • B05.89 - Other measles complications

  • B06 - Rubella [German measles]

    • B06.9 - Rubella without complication

  • B06.8 - Rubella with other complications

    • B06.81 - Rubella pneumonia

    • B06.89 - Other rubella complications

  • B08 - Other viral infections characterized by skin and mucous membrane lesions, not elsewhere classified

    • B08.3 - Erythema infectiosum [fifth disease]

    • B08.4 - Enteroviral vesicular stomatitis with exanthem

    • B08.8 - Other specified viral infections characterized by skin and mucous membrane lesions

  • B08.0 - Other orthopoxvirus infections

    • B08.04 - Paravaccinia, unspecified

    • B08.09 - Other orthopoxvirus infections

  • B08.01 - Cowpox and vaccinia not from vaccine

  • B08.2 - Exanthema subitum [sixth disease]

    • B08.20 - Exanthema subitum [sixth disease], unspecified

    • B08.21 - Exanthema subitum [sixth disease] due to human herpesvirus 6

    • B08.22 - Exanthema subitum [sixth disease] due to human herpesvirus 7

  • B08.6 - Parapoxvirus infections

    • B08.60 - Parapoxvirus infection, unspecified

    • B08.61 - Bovine stomatitis

    • B08.62 - Sealpox

    • B08.69 - Other parapoxvirus infections

  • B08.7 - Yatapoxvirus infections

    • B08.70 - Yatapoxvirus infection, unspecified

    • B08.71 - Tanapox virus disease

    • B08.72 - Yaba pox virus disease

    • B08.79 - Other yatapoxvirus infections

  • B25 - Cytomegaloviral disease

    • B25.8 - Other cytomegaloviral diseases

    • B25.9 - Cytomegaloviral disease, unspecified

  • B26 - Mumps

    • B26.9 - Mumps without complication

  • B26.8 - Mumps with other complications

  • B27.0 - Gammaherpesviral mononucleosis

    • B27.00 - Gammaherpesviral mononucleosis without complication

    • B27.01 - Gammaherpesviral mononucleosis with polyneuropathy

    • B27.02 - Gammaherpesviral mononucleosis with meningitis

    • B27.09 - Gammaherpesviral mononucleosis with other complications

  • B27.1 - Cytomegaloviral mononucleosis

    • B27.10 - Cytomegaloviral mononucleosis without complications

    • B27.11 - Cytomegaloviral mononucleosis with polyneuropathy

    • B27.12 - Cytomegaloviral mononucleosis with meningitis

    • B27.19 - Cytomegaloviral mononucleosis with other complication

  • B27.8 - Other infectious mononucleosis

    • B27.80 - Other infectious mononucleosis without complication

    • B27.81 - Other infectious mononucleosis with polyneuropathy

    • B27.82 - Other infectious mononucleosis with meningitis

    • B27.89 - Other infectious mononucleosis with other complication

  • B27.9 - Infectious mononucleosis, unspecified

    • 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

  • B33 - Other viral diseases, not elsewhere classified

    • B33.1 - Ross River disease

    • B33.3 - Retrovirus infections, not elsewhere classified

    • B33.4 - Hantavirus (cardio)-pulmonary syndrome [HPS] [HCPS]

    • B33.8 - Other specified viral diseases

  • B34 - Viral infection of unspecified site

    • B34.0 - Adenovirus infection, unspecified

    • B34.1 - Enterovirus infection, unspecified

    • B34.2 - Coronavirus infection, unspecified

    • B34.3 - Parvovirus infection, unspecified

    • B34.4 - Papovavirus infection, unspecified

    • B34.8 - Other viral infections of unspecified site

    • B34.9 - Viral infection, unspecified

  • B97 - Viral agents as the cause of diseases classified elsewhere

    • B97.0 - Adenovirus as the cause of diseases classified elsewhere

    • B97.4 - Respiratory syncytial virus as the cause of diseases classified elsewhere

    • B97.5 - Reovirus as the cause of diseases classified elsewhere

    • B97.6 - Parvovirus as the cause of diseases classified elsewhere

    • B97.7 - Papillomavirus as the cause of diseases classified elsewhere

  • B97.1 - Enterovirus as the cause of diseases classified elsewhere

    • B97.10 - Unspecified enterovirus as the cause of diseases classified elsewhere

    • B97.11 - Coxsackievirus as the cause of diseases classified elsewhere

    • B97.12 - Echovirus as the cause of diseases classified elsewhere

    • B97.19 - Other enterovirus as the cause of diseases classified elsewhere

  • B97.2 - Coronavirus as the cause of diseases classified elsewhere

    • B97.21 - SARS-associated coronavirus as the cause of diseases classified elsewhere

    • B97.29 - Other coronavirus as the cause of diseases classified elsewhere

  • B97.3 - Retrovirus as the cause of diseases classified elsewhere

    • B97.30 - Unspecified retrovirus as the cause of diseases classified elsewhere

    • B97.31 - Lentivirus as the cause of diseases classified elsewhere

    • B97.32 - Oncovirus as the cause of diseases classified elsewhere

    • B97.33 - Human T-cell lymphotrophic virus, type I [HTLV-I] as the cause of diseases classified elsewhere

    • B97.34 - Human T-cell lymphotrophic virus, type II [HTLV-II] as the cause of diseases classified elsewhere

    • B97.35 - Human immunodeficiency virus, type 2 [HIV 2] as the cause of diseases classified elsewhere

    • B97.39 - Other retrovirus as the cause of diseases classified elsewhere

  • B97.8 - Other viral agents as the cause of diseases classified elsewhere

    • B97.81 - Human metapneumovirus as the cause of diseases classified elsewhere

    • B97.89 - Other viral agents as the cause of diseases classified elsewhere

  • J09.X - Influenza due to identified novel influenza A virus

    • J09.X3 - Influenza due to identified novel influenza A virus with gastrointestinal manifestations

    • J09.X9 - Influenza due to identified novel influenza A virus with other manifestations

  • J10 - Influenza due to other identified influenza virus

    • J10.2 - Influenza due to other identified influenza virus with gastrointestinal manifestations

  • J10.8 - Influenza due to other identified influenza virus with other manifestations

    • J10.81 - Influenza due to other identified influenza virus with encephalopathy

    • J10.82 - Influenza due to other identified influenza virus with myocarditis

    • J10.83 - Influenza due to other identified influenza virus with otitis media

    • J10.89 - Influenza due to other identified influenza virus with other manifestations

  • J11 - Influenza due to unidentified influenza virus

    • J11.2 - Influenza due to unidentified influenza virus with gastrointestinal manifestations

  • J11.8 - Influenza due to unidentified influenza virus with other manifestations

    • J11.81 - Influenza due to unidentified influenza virus with encephalopathy

    • J11.82 - Influenza due to unidentified influenza virus with myocarditis

    • J11.83 - Influenza due to unidentified influenza virus with otitis media

    • J11.89 - Influenza due to unidentified influenza virus with other manifestations

  • L44 - Other papulosquamous disorders

    • L44.4 - Infantile papular acrodermatitis [Gianotti-Crosti]

  • T88.1 - Other complications following immunization, not elsewhere classified

    • T88.1XXA - Other complications following immunization, not elsewhere classified, initial encounter