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Volume 10, Number 8—August 2004

Research

Acute Encephalitis Hospitalizations, California, 1990–1999: Unrecognized Arboviral Encephalitis?

Rosalie T. Trevejo*Comments to Author 
Author affiliation: *Western University, Pomona, California, USA

Main Article

Table 1

Diagnoses for acute infectious or unspecified encephalitis among hospitalized patients in California, 1990–1999a

Diagnosis (ICD-9-CMb) No. of encephalitis diagnoses (%)c
Encephalitis of unspecified cause

Unspecified cause of encephalitis (323.9)
4,841 (34.7)
Unspecified non-arthropod-borne viral diseases of CNS (049.9)
2,932 (21.0)
Viral encephalitis with specified cause, not arboviral

Acute paralytic poliomyelitis specified as bulbar (045.0)
44 (0.3)
Other specified nonarthropodborne viral diseases of central nervous system (049.8)
288 (2.1)
Herpetic meningoencephalitis (054.3)
2,007 (14.4)
Encephalomyelitis due to rubella (056.01)
6 (0.04)
Rabies (071)
13 (0.1)
Mumps encephalitis (072.2)
14 (0.1)
Encephalitis in viral diseases classified elsewhere (323.0)
76 (0.5)
Other causes of encephalitis

Other encephalitis due to infection classified elsewhere (323.4)
117 (0.8)
Other causes of encephalitis (323.8)
2,196 (15.8)
Postinfectious causes of encephalitis

Postvaricella encephalitis (052.0)
421 (3.0)
Post measles encephalitis (055.0)
41 (0.3)
Postinfectious encephalitis (323.6)
595 (4.3)
Bacterial/rickettsial causes of encephalitis

Tuberculous encephalitis or myelitis (013.6)
30 (0.2)
Meningococcal encephalitis (036.1)
128 (0.9)
Syphilitic encephalitis (094.81)
11 (0.1)
Encephalitis in rickettsial diseases classified elsewhere (323.1)
0 (0)
Parasitic/protozoal causes of encephalitis

Meningoencephalitis attributable to toxoplasmosis (130.0)
82 (0.6)
Meningoencephalitis attributable to Naegleria (136.2)
10 (0.1)
Encephalitis in protozoal diseases classified elsewhere (323.2)
4 (0.03)
Arthropodborne viral encephalitis

Mosquitoborne viral encephalitis (062.0–062.9)
63 (0.5)
Tickborne viral encephalitis (063.0–063.9)
6 (0.04)
Viral encephalitis transmitted by other and unspecified arthropods (064)
14 (0.1)
Total no. of encephalitis diagnosesd 13,939

aPatients with a concurrent diagnosis of AIDS are excluded.
bInternational Classification of Diseases, 9th Revision, Clinical Modification.
cSource: Office of Statewide Health Planning and Development, Patient Discharge Data, Public Version A.
dTotal number of encephalitis diagnoses is greater than the number of encephalitis patients (n = 13,807) because some patients had two or more encephalitis diagnoses.

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