Table 1. Original set of 29 ICD-9 codes included in the influenzalike illness syndrome in ESSENCE*.
| ICD-9 code | Description | Specificity and severity rank† |
|---|---|---|
| 079.89 |
Viral infection NEC* |
4 |
| 079.99 |
Viral infection NOS* |
4 |
| 460 |
Nasopharyngitis, acute |
4 |
| 462 |
Pharyngitis, acute |
4 |
| 464.00 |
Laryngitis, acute, without obstruction |
4 |
| 464.10 |
Tracheitis, acute, without obstruction |
4 |
| 464.20 |
Laryngotracheitis, acute without obstruction |
4 |
| 465.0 |
Laryngopharyngitis, acute |
4 |
| 465.8 |
Infectious upper respiratory, multiple sites, acute NEC |
4 |
| 465.9 |
Infectious upper respiratory, multiple sites, acute NOS |
4 |
| 466.0 |
Bronchitis, acute |
3 |
| 466.11 |
Bronchiolitis due to respiratory syncytial virus |
3 |
| 466.19 |
Bronchiolitis, acute, due to other infectious organism |
3 |
| 478.9 |
Disease, upper respiratory NEC/NOS |
4 |
| 480.0 |
Pneumonia due to adenovirus |
2 |
| 480.1 |
Pneumonia due to respiratory syncytial virus |
2 |
| 480.2 |
Pneumonia due to parainfluenza |
2 |
| 480.8 |
Pneumonia due to virus NEC |
2 |
| 480.9 |
Viral pneumonia unspecified |
2 |
| 484.8 |
Pneumonia in other infectious disease NEC |
2 |
| 485 |
Bronchopneumonia, organism NOS |
2 |
| 486 |
Pneumonia, organism NOS |
2 |
| 487.0 |
Influenza with pneumonia |
1 |
| 487.1 |
Influenza with respiratory manifestation NEC |
1 |
| 487.8 |
Influenza with manifestation NEC |
1 |
| 490 |
Bronchitis NOS |
3 |
| 780.6 |
Fever |
4 |
| 784.1 |
Pain, throat |
4 |
| 786.2 | Cough | 4 |
*ICD-9, International Classification of Diseases, Ninth Revision; ESSENCE, Electronic Surveillance System for the Early Notification of Community-based Epidemics; NOS, not otherwise specified; NEC, not elsewhere classified. †Specificity and severity rank: 1, most severe or specific; 4, least severe or specific.