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Volume 15, Number 9—September 2009


Etiology of Encephalitis in Australia, 1990–2007

Clare Huppatz, David N. DurrheimComments to Author , Christopher Levi, Craig Dalton, David T. Williams, Mark S. Clements, and Paul M. Kelly
Author affiliations: Hunter New England Population Health, Newcastle, New South Wales, Australia (C. Huppatz, D.N. Durrheim, C. Dalton); Australian National University, Canberra, Australian Capital Territory, Australia (M.S. Clements, P.M. Kelly); John Hunter Hospital, New Lambton, New South Wales, Australia (C. Levi, D. Williams)

Main Article


Encephalitis-associated conditions with ICD-9-CM and ICD-10-AM codes most frequently used for primary encephalitis discharge diagnoses, New South Wales, Australia, 1990–2007*

Primary discharge diagnosis ICD code (ICD-9; ICD-10) No. hospitalizations (% of total)
All hospitalizations
5,926 (100)
Known pathogens 1,800 (30.6)
Herpes viral encephalitis (54.3; B00.4) 763 (12.9)
Varicella encephalitis (52.0; B01.1) 226 (3.8)
Toxoplasma meningoencephalitis (130.0; B58.2 ) 221(3.7)
Acute disseminated encephalitis (G04.0 in ICD-10) 136 (2.3)
Zoster encephalitis (B02.0 in ICD-10) 105 (1.8)
Subacute sclerosing panencephalitis (46.2; A81.1) 79 (1.3)
Other specified non–arthropod-borne viral diseases of the central nervous system (49.8; A85.8) 71 (1.2)
Enteroviral encephalitis (A85.0 in ICD-10) 49 (0.8)
Listerial meningitis and meningoencephalitis (A32.1 in ICD 10) 28 (0.5)
Encephalitis, myelitis, and encephalomyelitis –postinfectious encephalitis (323.6 in ICD-9) 18 (0.3)
Measles encephalitis (55.0 in ICD 9) 15 (0.3)
Encephalitis, myelitis, and encephalomyelitis –encephalitis in viral diseases classified elsewhere 
 (323.0 in ICD 9) 10 (0.2)
Rubella with neurologic complications –encephalomyelitis due to rubella (56.01 in ICD-9) 8 (0.1)
Meningococcal infection –meningococcal encephalitis (36.1 in ICD-9) 7 (0.1)
Viral encephalitis transmitted by other and unspecified arthropods (64 in ICD-9) 7 (0.1)
Bacterial meningoencephalitis and meningomyelitis, not elsewhere classified (G04.2 in ICD-10) 7 (0.1)
Mumps –mumps encephalitis (72.2 in ICD-9) 6 (0.1)
Other known pathogen codes (24 codes)
44 (0.7)
Unknown pathogens 4,126 (69.6)
Unspecified non–arthropod-borne viral diseases of the central nervous system or unspecified viral 
 encephalitis (49.9; A86) 2,218 (37.4)
Encephalitis, myelitis, and encephalomyelitis –unspecified cause of encephalitis (323.9; G04.9) 1,648 (28.8)
Encephalitis, myelitis, and encephalomyelitis –other cause of encephalitis (323.8; G04.8) 260 (4.4)

*ICD-9-CM, International Classification of Diseases, 9th Revision, Clinical Modification; ICD-10-AM, International Classification of Diseases, 10th Revision, Australian Modification.

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