The Virginia Department of Health (VDH) Office of Epidemiology collects and analyzes health data from emergency departments (EDs) to conduct public health surveillance. This page summarizes Virginia residents who sought care at EDs for unintentional overdose as identified by the chief complaint or discharge diagnosis.
- Rate Calculations: Overdose rates are presented as a rate per 10,000 ED visits. The total number of ED visits that occurred among Virginia residents of a city/county locality are used as the denominator to calculate this rate. This metric provides a consistent rate calculation across time when data reporting by EDs change (increases or decreases) as compared to the rate per 100,000 population.
- Suppression: Suppression is applied to overdose visit counts of 1 to 4 and rates with numerators of 1 to 4 to maintain confidentiality and accurate rate calculations. Suppressed statistics are indicated with an asterisk (*).
- Data Limitations: Data provide information on health trends rather than exact measure of overdoses in the community. You are encouraged to review the limitations of syndromic surveillance data: https://www.vdh.virginia.gov/surveillance-and-investigation/syndromic-surveillance/limitations/
- Sex and Age Restriction: Individuals with an unknown value for Sex or an age above 105 years will not be included in the Overdose Visits Rate by Age Category and Sex graph. These data will still be included in other components of the visualization.
The chief complaint is a free-text field that captures the patient’s primary reason for seeking medical care as interpreted by the ED registration staff. The discharge diagnosis is a coded field using standardized values defined by the International Classification of Diseases (ICD) 9th and 10th Revision or SNOMED Clinical Terms (CT) code sets.
ED visits are categorized into the following three unintentional drug overdose case definitions: 1) all drug overdose, 2) opioid or unspecified substance overdose, and 3) heroin overdose. VDH revises these case definitions based on guidance from the Centers for Disease Control and Prevention (CDC) and findings from ongoing data quality evaluations. Information on the current case definitions and case definition revisions, including historic definitions, can be found on the syndromic surveillance website:
Geographic location is assigned based on the patient’s residential zip code provided. A single zip code may span multiple city and county localities in Virginia. If a patient resides in a spanning zip code, the visit is assigned to the locality where the majority of the population resides. Virginia city and county populations combined to calculate an overdose rate per 10,000 ED visits because of zip codes spanning multiple localities can be found below.
Suppression is applied to overdose visit counts of 1 to 4 and rates with numerators of 1 to 4 to maintain confidentiality and accurate rate calculations. Suppressed statistics are indicated with an asterisk (*).
Further resources and data pertaining to drug overdose surveillance are available on this page: