West Nile Virus v1

Query purpose: 

Created by the CDC National Syndromic Surveillance Program (NSSP) for use with emergency department data to develop queries for all National Notifiable Diseases defined by the National Notifiable Diseases Surveillance System (NNDSS). Please note that while the disease queries are developed using the NNDSS case definition as the basis for identifying patient visits of interest, the queried patient visits themselves may or may not represent a case patient in NNDSS and further public health investigation will most often be required. This query is intended to be a version 1 and may be further improved upon by the NSSP community of practice in the future. This query is intended to be narrow and capture visits with specific terms to support greater monitoring and actionable public health data. However, given the seasonal occurrence and clinical features for West Nile virus disease are similar to other arthropod-borne viral disease (e.g., eastern equine encephalitis, Jamestown Canyon virus disease, La Crosse virus disease, Powassan, and St. Louis encephalitis), other conditions will likely be captured using this definition either due to similar clinical features eliciting West Nile virus disease to be considered in the differential or because of cross-reactivity in diagnostic assays. More complex and/or broader queries may exist that more broadly capture symptoms, travel-based terms, or similar arboviral diseases.

How it was developed: 

1. The CDC team used the NNDSS case definition of Arboviral diseases, neuroinvasive and non-neuroinvasive to identify SNOMED Clinical Terms (CT)) and chief complaint free-text for syndrome development, and West Nile specific diagnostic codes (International Classification of Diseases, 9th & 10th Revision (ICD-9-CM, ICD-10-CM),
2. The codes and free text were then categorized as inclusion or exclusion terms. These terms were formatted for querying in ESSENCE.
3. Text analysis was conducted on the initial query to find additional inclusion or exclusion terms.
4. The query was cross-checked internally by NSSP.

How it works:

The Chief Complaint Discharge Diagnosis (CCDD) parsed field is used to query both the discharge diagnosis codes and chief complaint free text, and exclusions are incorporated as necessary.

• Inclusion based on West Nile virus chief complaint free text terms:
  • The visit is included if it contains:
    1. A chief complaint related to disease name – (“west nile” or “westnile” or “WNV”) OR
• Inclusion based on ICD-10 discharge diagnosis codes related to West Nile virus:
  • The visit is included if it contains:
    1. A discharge diagnosis code for West Nile virus – (A92.3) OR
• Inclusion based on ICD-9 discharge diagnosis codes related to West Nile virus:
  • The visit is included if it contains:
    1. A discharge diagnosis code for West Nile virus – (066.40 or 066.41 or 066.42 or 066.49) OR
• Inclusion based on SNOMED discharge diagnosis codes related to West Nile virus:
  • The visit is included if it contains:
    1. A discharge diagnosis code for West Nile virus – (392662004 or 763018002) OR
    2. A discharge diagnosis code for West Nile virus variants – (397420007) OR
    3. A discharge diagnosis code for West Nile virus organism – (57311007) OR
    4. A discharge diagnosis code for conditions caused by West Nile – (404233006 or 417093003 or 430397002) ANDNOT
• All of the above must exclude:
  • A chief complaint related to history of West Nile virus infection – (“history of west nile” or “history of westnile” or “history west nile” or “history westnile” or “history of WNV” or “history WNV”)

Plain Language Description:

The definition uses discharge diagnosis codes and free-text chief complaint terms. The definition requires that an emergency department visit contains a reference to the disease by its discharge diagnosis code (in at least one of the following: ICD-10-CM, ICD-9-CM, SNOMED diagnostic codes), or by the disease or pathogen name listed in the chief complaint text. Therefore, the West Nile virus syndromic surveillance definition includes ICD-10-CM, ICD-9-CM, and SNOMED diagnostic codes for West Nile virus, along with direct mentions of West Nile virus (“west nile”, “westnile”, “WNV”) in chief complaint text. To ensure only acute West Nile virus infections were captured, chief complaint text indicating a history of West Nile was excluded.