Smallpox
In Viral infections characterized by skin and mucous membrane lesions (B00-B09), chapter 1: Certain Infectious and Parasitic Diseases
- B03 is billable and valid on claims for FY 2027. If the record has more detail, check the other codes under B00-B09 below.
- As a secondary diagnosis it is a CC (complication or comorbidity), which can raise the MS-DRG payment. It doesn't count when the principal diagnosis is one of 13 closely related codes.
- Doesn't count toward a Medicare Advantage risk score (no HCC in V28).
- AHRQ's Chronic Condition Indicator classes it as not chronic (an acute or short-term condition).
Also indexed as: Alastrim; Smallpox; Variola; Varioloid
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Official coding guidelines
From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.
Rules for coding infections and parasitic diseases, including HIV, organism and drug resistance codes, sepsis and septic shock, MRSA, Zika, and COVID-19.
- Human Immunodeficiency Virus (HIV) Infections (page 19)
- Infectious agents as the cause of diseases classified to other chapters (page 22)
- Infections resistant to antibiotics (page 22)
- Sepsis, Severe Sepsis, and Septic Shock (page 23)
- Methicillin Resistant Staphylococcus aureus (MRSA) Conditions (page 27)
- Zika virus infections (page 28)
- Coronavirus infections (page 28)
Other codes under B00-B09
Viral infections characterized by skin and mucous membrane lesions (B00-B09)
- B00Herpesviral [herpes simplex] infections
- B01Varicella [chickenpox]
- B02Zoster [herpes zoster]
- B03Smallpox(this code)
- B04Monkeypox
- B05Measles
- B06Rubella [German measles]
- B07Viral warts
- B08Other viral infections characterized by skin and mucous membrane lesions, not elsewhere classified
- B09Unspecified viral infection characterized by skin and mucous membrane lesions
B03 MS-DRGs
As the principal diagnosis, B03 groups to MS-DRG 865 or 866 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.
Related conditions
Grouped by AHRQ's Clinical Classifications Software Refined (CCSR), which sorts every diagnosis code into clinically meaningful categories.
B03 is in Viral infection (INF008, its default category), with 309 codes. Others in it:
About the condition
Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.
Smallpox
Smallpox is a disease caused by the Variola major virus. Some experts say that over the centuries it has killed more people than all other infectious diseases combined. Worldwide vaccination stopped the spread of smallpox three decades ago. The last case was reported in 1977. Two research labs still keep small amounts of the virus. Experts fear bioterrorists could use the virus to spread disease.
Read more about smallpox on MedlinePlusCode history
Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.
ICD-9-CM equivalent
Legacy crosswalk from the CMS General Equivalence Mappings (last updated 2018).
- 050.0 Variola major (approximate)
- 050.1 Alastrim (approximate)
- 050.9 Smallpox, unspecified (approximate)