Volume 10, Number 8—August 2004
Research
Acute Encephalitis Hospitalizations, California, 1990–1999: Unrecognized Arboviral Encephalitis?
Rosalie T. Trevejo*
Table 3
Diagnoses and month of admission for patients hospitalized with acute infectious or unspecified encephalitis in selected California counties, 1991–1999
| Sacramento-Yolo | Sutter-Yuba | Imperial- Riverside | |
|---|---|---|---|
| 1995 Population estimates |
1,271,500 |
135,400 |
1,500,300 |
| Diagnosis (ICD-9-CMa) |
No. of encephalitis diagnoses (%)b |
||
| Encephalitis of unspecified cause |
305 (60.2) |
45 (70.3) |
338 (58.2) |
| Viral encephalitis with specified cause, not arboviral |
74 (14.6) |
11 (17.2) |
112 (19.4) |
| Other causes of encephalitis |
76 (15.0) |
5 (7.8) |
64 (11.1) |
| Postinfectious causes of encephalitis |
38 (7.5) |
1 (1.6) |
45 (7.8) |
| Bacterial/rickettsial causes of encephalitis |
10 (2.0) |
0 (0) |
7 (1.2) |
| Parasitic/protozoal causes of encephalitis |
2 (0.4) |
1 (1.6) |
5 (0.09) |
| Arthropodborne viral encephalitisc |
2 (0.4) |
1 (1.6) |
7 (1.2) |
| Total no. of encephalitis diagnosesd |
507 |
64 |
578 |
| Month of hospital admission |
No. of admissions (%) |
||
| January–March |
112 (22.1) |
17 (26.6) |
160 (28.0) |
| April–June |
126 (24.9) |
12 (18.8) |
127 (22.2) |
| July–September |
139 (27.5) |
15 (23.4) |
140 (24.5) |
| October–December |
129 (25.5) |
20 (31.3) |
145 (25.3) |
| Overall | 506 (100) | 64 (100) | 572 (100) |
aInternational Classification of Diseases, 9th Revision, Clinical Modification.
bSource: Office of Statewide Health Planning and Development, Patient Discharge Data, Public Version A.
cArboviral encephalitis was diagnosed in Sacramento in 1992 (n = 1) and 1997 (n = 1), in Yuba in 1999 (n = 1), in Imperial in 1997 (n = 1), and in Riverside in 1991 (n = 3), 1994 (n = 2), and 1997 (n = 1).
dTotal number of encephalitis diagnoses in Sacramento-Yolo and Imperial-Riverside is greater than the number of encephalitis patients because some patients had two or more encephalitis diagnoses.
