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ICD-10-CM 2027

ICD-10 code for infection

B99.9

Unspecified infectious disease

✓ Billable / specific

From the official ICD-10-CM alphabetic index entry “Infection, infected, infective (opportunistic)”. Page updated September 29, 2026.

About coding infection

The ICD-10-CM code for infection is B99.9 (Unspecified infectious disease). The official index lists 224+ more specific codes, so check the documentation for details such as type, cause, site or severity before settling on B99.9.

Within B99, choose B99.9 (Unspecified infectious disease) only when documentation doesn't support a more specific option: other infectious disease (B99.8).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC, relative weight 2.1859), DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC, relative weight 1.0235) and DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC, relative weight 0.6787), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

More specific infection codes (official index)

  • with
  • drug resistant organism
  • lymphangitis
  • organ dysfunction (acute) R65.20 — Severe sepsis without septic shock
  • with septic shock R65.21 — Severe sepsis with septic shock
  • abscess (skin) - code by site under Abscess
  • Absidia
  • Acanthamoeba
  • Acanthocheilonema (perstans) (streptocerca) B74.4 — Mansonelliasis
  • accessory sinus (chronic)
  • achorion
  • Acinetobacter baumannii, as cause of disease classified elsewhere B96.83 — Acinetobacter baumannii as the cause of diseases classified elsewhere
  • Acremonium falciforme B47.0 — Eumycetoma
  • acromioclavicular M00.9 — Pyogenic arthritis, unspecified
  • Actinobacillus (actinomycetem-comitans) A28.8 — Other specified zoonotic bacterial diseases, not elsewhere classified
  • mallei A24.0 — Glanders
  • muris A25.1 — Streptobacillosis
  • Actinomadura B47.1 — Actinomycetoma
  • Actinomyces (israelii) A42.9 — Actinomycosis, unspecified
  • Actinomycetales
  • actinomycotic NOS
  • adenoid (and tonsil) J03.90 — Acute tonsillitis, unspecified
  • chronic J35.02 — Chronic adenoiditis
  • adenovirus NEC
  • as cause of disease classified elsewhere B97.0 — Adenovirus as the cause of diseases classified elsewhere
  • unspecified nature or site B34.0 — Adenovirus infection, unspecified
  • aerogenes capsulatus A48.0 — Gas gangrene
  • aertrycke
  • alimentary canal NOS
  • Allescheria boydii B48.2 — Allescheriasis
  • Alternaria B48.8 — Other specified mycoses
  • alveolus, alveolar (process) K04.7 — Periapical abscess without sinus
  • Ameba, amebic (histolytica)
  • amniotic fluid, sac or cavity O41.10 — Infection of amniotic sac and membranes, unspecified
  • chorioamnionitis O41.12 — Chorioamnionitis
  • placentitis O41.14 — Placentitis
  • amputation stump (surgical)
  • Ancylostoma (duodenalis) B76.0 — Ancylostomiasis
  • Anisakiasis, Anisakis larvae B81.0 — Anisakiasis
  • anthrax
  • antrum (chronic)
  • anus, anal (papillae) (sphincter) K62.89 — Other specified diseases of anus and rectum
  • arbovirus (arbor virus) A94 — Unspecified arthropod-borne viral fever
  • specified type NEC A93.8 — Other specified arthropod-borne viral fevers
  • artificial insemination N98.0 — Infection associated with artificial insemination
  • Ascaris lumbricoides
  • Ascomycetes B47.0 — Eumycetoma
  • Aspergillus (flavus) (fumigatus) (terreus)
  • atypical
  • acid-fast (bacilli)
  • mycobacteria
  • virus A81.9 — Atypical virus infection of central nervous system, unspecified
  • specified type NEC A81.89 — Other atypical virus infections of central nervous system
  • auditory meatus (external)
  • auricle (ear)
  • axillary gland (lymph) L04.2 — Acute lymphadenitis of upper limb
  • Bacillus A49.9 — Bacterial infection, unspecified
  • abortus A23.1 — Brucellosis due to Brucella abortus
  • anthracis
  • ducreyi (any location) A57 — Chancroid
  • Flexner's A03.1 — Shigellosis due to Shigella flexneri
  • Friedländer's NEC A49.8 — Other bacterial infections of unspecified site
  • gas (gangrene) A48.0 — Gas gangrene
  • mallei A24.0 — Glanders
  • melitensis A23.0 — Brucellosis due to Brucella melitensis
  • paratyphoid, paratyphosus A01.4 — Paratyphoid fever, unspecified
  • A A01.1 — Paratyphoid fever A
  • B A01.2 — Paratyphoid fever B
  • C A01.3 — Paratyphoid fever C
  • Shiga (-Kruse) A03.0 — Shigellosis due to Shigella dysenteriae
  • suipestifer
  • swimming pool A31.1 — Cutaneous mycobacterial infection
  • typhosa A01.00 — Typhoid fever, unspecified
  • welchii
  • bacterial NOS A49.9 — Bacterial infection, unspecified
  • as cause of disease classified elsewhere B96.89 — Other specified bacterial agents as the cause of diseases classified elsewhere
  • Acinetobacter baumannii B96.83 — Acinetobacter baumannii as the cause of diseases classified elsewhere
  • Bacteroides fragilis [B. fragilis] B96.6 — Bacteroides fragilis [B. fragilis] as the cause of diseases classified elsewhere
  • Clostridium perfringens [C. perfringens] B96.7 — Clostridium perfringens [C. perfringens] as the cause of diseases classified elsewhere
  • Cronobacter (sakazakii) A49.8 — Other bacterial infections of unspecified site
  • Enterobacter sakazakii B96.89 — Other specified bacterial agents as the cause of diseases classified elsewhere
  • Enterococcus B95.2 — Enterococcus as the cause of diseases classified elsewhere
  • Escherichia coli [E. coli] B96.20 — Unspecified Escherichia coli [E. coli] as the cause of diseases classified elsewhere
  • Helicobacter pylori [H.pylori] B96.81 — Helicobacter pylori [H. pylori] as the cause of diseases classified elsewhere
  • Hemophilus influenzae [H. influenzae] B96.3 — Hemophilus influenzae [H. influenzae] as the cause of diseases classified elsewhere
  • Klebsiella pneumoniae [K. pneumoniae] B96.1 — Klebsiella pneumoniae [K. pneumoniae] as the cause of diseases classified elsewhere
  • Mycoplasma pneumoniae [M. pneumoniae] B96.0 — Mycoplasma pneumoniae [M. pneumoniae] as the cause of diseases classified elsewhere
  • Proteus (mirabilis) (morganii) B96.4 — Proteus (mirabilis) (morganii) as the cause of diseases classified elsewhere
  • Pseudomonas (aeruginosa) (mallei) (pseudomallei) B96.5 — Pseudomonas (aeruginosa) (mallei) (pseudomallei) as the cause of diseases classified elsewhere
  • Staphylococcus B95.8 — Unspecified staphylococcus as the cause of diseases classified elsewhere
  • aureus (methicillin susceptible) (MSSA) B95.61 — Methicillin susceptible Staphylococcus aureus infection as the cause of diseases classified elsewhere
  • methicillin resistant (MRSA) B95.62 — Methicillin resistant Staphylococcus aureus infection as the cause of diseases classified elsewhere
  • specified NEC B95.7 — Other staphylococcus as the cause of diseases classified elsewhere
  • Streptococcus B95.5 — Unspecified streptococcus as the cause of diseases classified elsewhere
  • group A B95.0 — Streptococcus, group A, as the cause of diseases classified elsewhere
  • group B B95.1 — Streptococcus, group B, as the cause of diseases classified elsewhere
  • pneumoniae B95.3 — Streptococcus pneumoniae as the cause of diseases classified elsewhere
  • specified NEC B95.4 — Other streptococcus as the cause of diseases classified elsewhere
  • Vibrio vulnificus B96.82 — Vibrio vulnificus as the cause of diseases classified elsewhere
  • specified NEC A48.8 — Other specified bacterial diseases
  • Bacterium
  • paratyphosum A01.4 — Paratyphoid fever, unspecified
  • A A01.1 — Paratyphoid fever A
  • B A01.2 — Paratyphoid fever B
  • C A01.3 — Paratyphoid fever C
  • typhosum A01.00 — Typhoid fever, unspecified
  • Bacteroides NEC A49.8 — Other bacterial infections of unspecified site
  • fragilis, as cause of disease classified elsewhere B96.6 — Bacteroides fragilis [B. fragilis] as the cause of diseases classified elsewhere
  • Balantidium coli A07.0 — Balantidiasis
  • Bartholin's gland N75.8 — Other diseases of Bartholin's gland
  • Basidiobolus B46.8 — Other zygomycoses
  • bile duct (common) (hepatic)
  • bladder
  • Blastomyces, blastomycotic
  • brasiliensis
  • dermatitidis
  • European
  • Loboi B48.0 — Lobomycosis
  • North American B40.9 — Blastomycosis, unspecified
  • South American
  • bleb, postprocedure
  • bone
  • Bordetella
  • Borrelia bergdorfi A69.20 — Lyme disease, unspecified
  • brain G04.90 — Encephalitis and encephalomyelitis, unspecified
  • membranes
  • septic G06.0 — Intracranial abscess and granuloma
  • meninges
  • branchial cyst Q18.0 — Sinus, fistula and cyst of branchial cleft
  • breast
  • bronchus
  • Brucella A23.9 — Brucellosis, unspecified
  • abortus A23.1 — Brucellosis due to Brucella abortus
  • canis A23.3 — Brucellosis due to Brucella canis
  • melitensis A23.0 — Brucellosis due to Brucella melitensis
  • mixed A23.8 — Other brucellosis
  • specified NEC A23.8 — Other brucellosis
  • suis A23.2 — Brucellosis due to Brucella suis
  • Brugia (malayi) B74.1 — Filariasis due to Brugia malayi
  • timori B74.2 — Filariasis due to Brugia timori
  • bursa
  • buttocks (skin) L08.9 — Local infection of the skin and subcutaneous tissue, unspecified
  • Campylobacter, intestinal A04.5 — Campylobacter enteritis
  • as cause of disease classified elsewhere B96.81 — Helicobacter pylori [H. pylori] as the cause of diseases classified elsewhere
  • Candida (albicans) (tropicalis)
  • candiru B88.8 — Other specified infestations
  • Capillaria (intestinal) B81.1 — Intestinal capillariasis
  • hepatica B83.8 — Other specified helminthiases
  • philippinensis B81.1 — Intestinal capillariasis
  • cartilage
  • catheter-related bloodstream (CRBSI) T80.211 — Bloodstream infection due to central venous catheter
  • cat liver fluke B66.0 — Opisthorchiasis
  • cellulitis - code by site under Cellulitis
  • central line-associated T80.219 — Unspecified infection due to central venous catheter
  • bloodstream (CLABSI) T80.211 — Bloodstream infection due to central venous catheter
  • specified NEC T80.218 — Other infection due to central venous catheter
  • Cephalosporium falciforme B47.0 — Eumycetoma
  • cerebrospinal
  • cervical gland (lymph) L04.0 — Acute lymphadenitis of face, head and neck
  • cervix
  • cesarean delivery wound (puerperal) O86.00 — Infection of obstetric surgical wound, unspecified
  • cestodes
  • chest J22 — Unspecified acute lower respiratory infection
  • Chilomastix (intestinal) A07.8 — Other specified protozoal intestinal diseases
  • Chlamydia, chlamydial A74.9 — Chlamydial infection, unspecified
  • anus A56.3 — Chlamydial infection of anus and rectum
  • genitourinary tract A56.2 — Chlamydial infection of genitourinary tract, unspecified
  • lower A56.00 — Chlamydial infection of lower genitourinary tract, unspecified
  • specified NEC A56.19 — Other chlamydial genitourinary infection
  • lymphogranuloma A55 — Chlamydial lymphogranuloma (venereum)
  • pharynx A56.4 — Chlamydial infection of pharynx
  • psittaci A70 — Chlamydia psittaci infections
  • rectum A56.3 — Chlamydial infection of anus and rectum
  • sexually transmitted NEC A56.8 — Sexually transmitted chlamydial infection of other sites
  • cholera
  • Cladosporium
  • bantianum (brain abscess) B43.1 — Pheomycotic brain abscess
  • carrionii B43.0 — Cutaneous chromomycosis
  • castellanii B36.1 — Tinea nigra
  • trichoides (brain abscess) B43.1 — Pheomycotic brain abscess
  • werneckii B36.1 — Tinea nigra
  • Clonorchis (sinensis) (liver) B66.1 — Clonorchiasis
  • Clostridioides
  • difficile
  • as cause of disease classified elsewhere B96.89 — Other specified bacterial agents as the cause of diseases classified elsewhere
  • foodborne (disease)
  • not specified as recurrent A04.72 — Enterocolitis due to Clostridium difficile, not specified as recurrent
  • recurrent A04.71 — Enterocolitis due to Clostridium difficile, recurrent
  • gas gangrene A48.0 — Gas gangrene
  • necrotizing enterocolitis
  • not specified as recurrent A04.72 — Enterocolitis due to Clostridium difficile, not specified as recurrent
  • recurrent A04.71 — Enterocolitis due to Clostridium difficile, recurrent
  • sepsis A41.4 — Sepsis due to anaerobes
  • Clostridium NEC
  • bifermentans A48.0 — Gas gangrene
  • botulinum (food poisoning) A05.1 — Botulism food poisoning
  • infant A48.51 — Infant botulism
  • wound A48.52 — Wound botulism
  • difficile
  • as cause of disease classified elsewhere B96.89 — Other specified bacterial agents as the cause of diseases classified elsewhere
  • foodborne (disease)
  • not specified as recurrent A04.72 — Enterocolitis due to Clostridium difficile, not specified as recurrent
  • recurrent A04.71 — Enterocolitis due to Clostridium difficile, recurrent
  • gas gangrene A48.0 — Gas gangrene
  • necrotizing enterocolitis
  • not specified as recurrent A04.72 — Enterocolitis due to Clostridium difficile, not specified as recurrent
  • recurrent A04.71 — Enterocolitis due to Clostridium difficile, recurrent
  • sepsis A41.4 — Sepsis due to anaerobes
  • gas-forming NEC A48.0 — Gas gangrene
  • histolyticum A48.0 — Gas gangrene
  • novyi, causing gas gangrene A48.0 — Gas gangrene
  • oedematiens A48.0 — Gas gangrene
  • perfringens
  • as cause of disease classified elsewhere B96.7 — Clostridium perfringens [C. perfringens] as the cause of diseases classified elsewhere
  • due to food A05.2 — Foodborne Clostridium perfringens [Clostridium welchii] intoxication
  • foodborne (disease) A05.2 — Foodborne Clostridium perfringens [Clostridium welchii] intoxication
  • gas gangrene A48.0 — Gas gangrene
  • sepsis A41.4 — Sepsis due to anaerobes
  • septicum, causing gas gangrene A48.0 — Gas gangrene
  • sordellii, causing gas gangrene A48.0 — Gas gangrene
  • welchii
  • as cause of disease classified elsewhere B96.7 — Clostridium perfringens [C. perfringens] as the cause of diseases classified elsewhere
  • foodborne (disease) A05.2 — Foodborne Clostridium perfringens [Clostridium welchii] intoxication
  • gas gangrene A48.0 — Gas gangrene
  • necrotizing enteritis A05.2 — Foodborne Clostridium perfringens [Clostridium welchii] intoxication
  • sepsis A41.4 — Sepsis due to anaerobes
  • Coccidioides (immitis)
  • colon
  • colostomy K94.02 — Colostomy infection
  • common duct
  • congenital P39.9 — Infection specific to the perinatal period, unspecified
  • Candida (albicans) P37.5 — Neonatal candidiasis
  • cytomegalovirus P35.1 — Congenital cytomegalovirus infection
  • hepatitis, viral P35.3 — Congenital viral hepatitis
  • herpes simplex P35.2 — Congenital herpesviral [herpes simplex] infection
  • infectious or parasitic disease P37.9 — Congenital infectious or parasitic disease, unspecified
  • specified NEC P37.8 — Other specified congenital infectious and parasitic diseases
  • listeriosis (disseminated) P37.2 — Neonatal (disseminated) listeriosis
  • malaria NEC P37.4 — Other congenital malaria
  • falciparum P37.3 — Congenital falciparum malaria
  • Plasmodium falciparum P37.3 — Congenital falciparum malaria
  • poliomyelitis P35.8 — Other congenital viral diseases
  • rubella P35.0 — Congenital rubella syndrome
  • skin P39.4 — Neonatal skin infection
  • toxoplasmosis (acute) (subacute) (chronic) P37.1 — Congenital toxoplasmosis
  • tuberculosis P37.0 — Congenital tuberculosis
  • urinary (tract) P39.3 — Neonatal urinary tract infection
  • vaccinia P35.8 — Other congenital viral diseases
  • virus P35.9 — Congenital viral disease, unspecified
  • specified type NEC P35.8 — Other congenital viral diseases
  • Conidiobolus B46.8 — Other zygomycoses
  • coronavirus-2019 U07.1 — COVID-19
  • coronavirus NEC B34.2 — Coronavirus infection, unspecified
  • as cause of disease classified elsewhere B97.29 — Other coronavirus as the cause of diseases classified elsewhere
  • severe acute respiratory syndrome (SARS associated) B97.21 — SARS-associated coronavirus as the cause of diseases classified elsewhere
  • corpus luteum
  • Corynebacterium diphtheriae
  • cotia virus B08.8 — Other specified viral infections characterized by skin and mucous membrane lesions
  • COVID-19 U07.1 — COVID-19
  • Coxiella burnetii A78 — Q fever
  • coxsackie
  • Cronobacter (sakazakii) A49.8 — Other bacterial infections of unspecified site
  • as cause of disease classified elsewhere B96.89 — Other specified bacterial agents as the cause of diseases classified elsewhere
  • generalized A41.59 — Other Gram-negative sepsis
  • Cryptococcus neoformans
  • Cryptosporidium A07.2 — Cryptosporidiosis
  • Cunninghamella
  • cyst
  • cystic duct K81.9 — Cholecystitis, unspecified
  • Cysticercus cellulosae
  • cytomegalovirus, cytomegaloviral B25.9 — Cytomegaloviral disease, unspecified
  • congenital P35.1 — Congenital cytomegalovirus infection
  • maternal, maternal care for (suspected) damage to fetus O35.3 — Maternal care for (suspected) damage to fetus from viral disease in mother
  • mononucleosis B27.10 — Cytomegaloviral mononucleosis without complications
  • with
  • complication NEC B27.19 — Cytomegaloviral mononucleosis with other complication
  • meningitis B27.12 — Cytomegaloviral mononucleosis with meningitis
  • polyneuropathy B27.11 — Cytomegaloviral mononucleosis with polyneuropathy
  • delta-agent (acute), in hepatitis B carrier B17.0 — Acute delta-(super) infection of hepatitis B carrier
  • dental (pulpal origin) K04.7 — Periapical abscess without sinus
  • Deuteromycetes B47.0 — Eumycetoma
  • Dicrocoelium dendriticum B66.2 — Dicroceliasis
  • Dipetalonema (perstans) (streptocerca) B74.4 — Mansonelliasis
  • diphtherial
  • Diphyllobothrium (adult) (latum) (pacificum) B70.0 — Diphyllobothriasis
  • larval B70.1 — Sparganosis
  • Diplogonoporus (grandis) B71.8 — Other specified cestode infections
  • Dipylidium caninum B67.4 — Echinococcus granulosus infection, unspecified
  • Dirofilaria B74.8 — Other filariases
  • Dracunculus medinensis B72 — Dracunculiasis
  • Drechslera (hawaiiensis) B43.8 — Other forms of chromomycosis
  • ducreyi Haemophilus (any location) A57 — Chancroid
  • due to or resulting from
  • artificial insemination N98.0 — Infection associated with artificial insemination
  • Babesia
  • divergens (-like) strain B60.03 — Babesiosis due to Babesia divergens
  • duncani (-type) species B60.02 — Babesiosis due to Babesia duncani
  • microti B60.01 — Babesiosis due to Babesia microti
  • species
  • specified NEC B60.09 — Other babesiosis

See all 1170 entries in the alphabetic index

Common questions about infection ICD-10 codes

What is the ICD-10 code for infection?

B99.9 — Unspecified infectious disease. More specific codes apply when the documentation supports them: R65.20, R65.21, B74.4, B96.83 and others below.

What is the ICD-10 code for acanthocheilonema infection?

B74.4 — Mansonelliasis.

What is the ICD-10 code for acremonium falciforme infection?

B47.0 — Eumycetoma.

What is the ICD-10 code for acromioclavicular infection?

M00.9 — Pyogenic arthritis, unspecified.

What is the ICD-10 code for actinobacillus infection?

A28.8 — Other specified zoonotic bacterial diseases, not elsewhere classified.

What is the ICD-10 code for actinomadura infection?

B47.1 — Actinomycetoma.

What is the ICD-10 code for actinomyces infection?

A42.9 — Actinomycosis, unspecified.

Is B99.9 billable?

Yes. B99.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).

Can B99.9 be used as a principal diagnosis?

Yes. The Medicare Code Editor doesn't restrict B99.9 as a principal diagnosis.

Is B99.9 a CC or MCC?

No. B99.9 is neither a CC nor an MCC under MS-DRG v44.0.