Every disease, symptom, and medical condition has a unique code in the ICD-10-CM system, which stands for International Classification of Diseases, 10th Revision, Clinical Modification. Hospitals and clinics use these codes to bill insurance companies. The code on your Explanation of Benefits (EOB) tells the insurer what your doctor treated you for. Understanding these codes helps you catch billing errors before they cost you money.
B00 Herpesviral (Herpes Simplex) Infections
Definition
ICD-10-CM code B00 covers all infections caused by the Herpes Simplex Virus (HSV). There are two main types: HSV-1 usually causes oral herpes, commonly known as cold sores, and HSV-2 usually causes genital herpes. Once HSV enters the body, it stays there permanently. The virus hides in nerve cells and can reactivate at any time.
The code B00 has several sub-codes. B00.0 covers eczema herpeticum. B00.1 covers herpetic vesicular dermatitis. B00.2 covers herpetic gingivostomatitis. B00.3 covers herpetic meningitis. B00.4 covers herpetic encephalitis. B00.5 covers herpetic ocular disease. B00.7 covers disseminated herpetic disease. B00.9 covers unspecified herpesviral infection.
Coders must choose the most specific sub-code available. Using B00.9 when a more specific code exists is a common billing error that insurance companies flag.
Real-World Billing Example
Patient: 37-year-old female visits urgent care.
Complaint: Painful blisters on lower lip, fever, and swollen glands.
Diagnosis: Doctor documents herpetic gingivostomatitis.
Correct Code: B00.2 — Herpetic gingivostomatitis and pharyngotonsillitis.
Common Billing Error: Coder submits B00.9 instead of B00.2. The claim pays at a lower rate and the patient ends up paying a higher out-of-pocket cost.
Why It Matters: Specific codes trigger accurate reimbursement. Unspecified codes often attract audits.
B01 Varicella (Chickenpox)
Definition
ICD-10-CM code B01 covers varicella, the primary infection caused by the Varicella-Zoster Virus (VZV), commonly known as chickenpox. It spreads easily through air and direct contact with blisters.
Sub-codes include B01.0 for varicella meningitis, B01.1 for varicella encephalitis, B01.11 for post-chickenpox encephalitis, B01.12 for post-chickenpox myelitis, B01.2 for varicella pneumonia, B01.8 for other complications, and B01.9 for varicella without complication.
If a patient develops complications, the coder must use the complication-specific sub-code. Billing B01.9 for a patient who has varicella pneumonia is an undercoding error, reducing reimbursement.
Real-World Billing Example
Patient: 8-year-old boy admitted to hospital.
Complaint: Chickenpox rash with breathing difficulty for 2 days.
Diagnosis: Pediatrician documents varicella pneumonia.
Correct Code: B01.2 — Varicella pneumonia.
Common Billing Error: Billing B01.9 due to missing documentation of pneumonia. Hospitals receive lower reimbursement.
B02 Zoster (Herpes Zoster / Shingles)
Definition
ICD-10-CM code B02 covers herpes zoster, or shingles, which is a reactivation of the Varicella-Zoster Virus. Stress, aging, or a weakened immune system can trigger the virus to reactivate.
Sub-codes include B02.0 for zoster encephalitis, B02.1 for zoster meningitis, B02.2 for zoster with other nervous system involvement, B02.21 for postherpetic geniculate ganglionitis, B02.22 for postherpetic trigeminal neuralgia, B02.23 for postherpetic polyneuropathy, B02.24 for postherpetic myelitis, B02.29 for other postherpetic nervous system involvement, B02.3 for zoster ocular disease, B02.31 for zoster conjunctivitis, B02.32 for zoster iridocyclitis, B02.33 for zoster keratitis, B02.34 for zoster scleritis, B02.39 for other herpes zoster eye disease, B02.7 for disseminated zoster, B02.8 for other complications, and B02.9 for zoster without complication.
Postherpetic neuralgia is a serious complication where nerve pain persists long after the rash resolves. Coders must capture these codes separately.
Real-World Billing Example
Patient: 62-year-old male, follow-up 6 weeks after shingles.
Complaint: Burning nerve pain on left side of chest.
Diagnosis: Postherpetic polyneuropathy.
Correct Code: B02.23 — Postherpetic polyneuropathy.
Common Billing Error: Coder uses B02.9 after rash resolves, leaving chronic nerve pain uncoded.
B03 Smallpox
Definition
ICD-10-CM code B03 covers smallpox, caused by the Variola virus. The disease was eradicated in 1980. This code exists primarily for bioterrorism preparedness, research, and historical records.
Real-World Billing Example
Scenario: Researcher handles archived samples in a BSL-4 lab.
Incident: Potential exposure.
Documentation: Physician documents potential smallpox exposure.
Correct Code: B03 for confirmed cases. Suspected exposure uses Z20.89.
B04 Monkeypox
Definition
ICD-10-CM code B04 covers monkeypox (mpox), caused by the Monkeypox virus. Symptoms include fever, rash, and swollen lymph nodes. The 2022 global outbreak made B04 widely used.
Real-World Billing Example
Patient: 29-year-old male presents with rash and fever.
Test Result: PCR confirms monkeypox.
Correct Code: B04 after laboratory confirmation.
Common Billing Error: Billing B04 before test results leads to rejected claims.
B05 Measles
Definition
ICD-10-CM code B05 covers measles, caused by Measles morbillivirus. Measles is extremely contagious. Sub-codes include B05.0 for measles with encephalitis, B05.1 for measles with meningitis, B05.2 for measles with pneumonia, B05.3 for measles with otitis media, B05.4 for intestinal complications, B05.8 for other complications, and B05.9 for measles without complication.
Real-World Billing Example
Patient: 5-year-old unvaccinated child.
Complaint: Fever, red eyes, white spots in mouth, spreading rash.
Diagnosis: Measles with secondary ear infection.
Correct Code: B05.3 — Measles complicated by otitis media.
Common Billing Error: Coding separately for B05.9 and otitis media, creating conflict.
B06 Rubella (German Measles)
Definition
ICD-10-CM code B06 covers rubella, caused by the Rubella virus. Sub-codes include B06.0 for rubella with neurological complications, B06.01 for rubella encephalitis, B06.02 for rubella meningitis, B06.8 for other complications, and B06.9 for rubella without complication. Congenital rubella syndrome is coded separately as P35.0.
Real-World Billing Example
Patient: 26-year-old pregnant woman exposed to rubella.
Correct Codes: Z20.4 for exposure + O98.519 for viral diseases complicating pregnancy. B06 should not be used unless infection is confirmed.
B07 Viral Warts
Definition
ICD-10-CM code B07 covers viral warts caused by Human Papillomavirus (HPV). Sub-codes include B07.0 for plantar wart, B07.8 for other viral warts, and B07.9 for unspecified viral wart. Anogenital warts use a different code, A63.0.
Real-World Billing Example
Patient: 19-year-old college student with plantar wart.
Correct Code: B07.0 — Plantar wart.
Common Billing Errors: Using B07.9 instead of B07.0, or B07.8 for anogenital warts instead of A63.0.
How to Use This Knowledge as a Patient
- Request an itemized bill.
- Look up every B-code on your EOB using the CMS ICD-10 lookup tool.
- Verify that the code matches your doctor’s documentation.
- If the code is more severe than your condition, contact the billing department for correction.
- Keep copies of all EOBs for at least seven years.
This article is for patient education purposes only. Always consult a certified medical coder or your provider for specific billing disputes.
