The third approach used for the assessments included various spatial epidemiology methods. The most common form of spatial epidemiology used as part of opioid-related vulnerability was the choropleth map, which maps a variable using color intensity. ColorBrewer is a useful resource for identifying appropriate color schemes including sequential (for increasing rates), diverging (for comparing above and below a baseline), and qualitative (using no meaningful sort order for outcomes). Figure 6 illustrates per capita income from the American Community Survey using a sequential yellow-orange-red color scheme, mapped using R and Leaflet and uploaded to RPubs, a public website for visualizations created in R.
While most jurisdictions used county-level data, some jurisdictions focused on smaller geographic units, such as ZIP code-level data (ZIP code tabulation area) and formatted it for mapping purposes such that low population ZIP codes could be merged with adjacent ZIP codes to facilitate more stable rate calculations.
Additionally, jurisdictions introduced point layers including physical address-level data consisting of: buprenorphine-waivered physicians, syringe service programs, Naloxone providers, drug detox, outpatient and inpatient services, and other community-based resources. This type of approach added community health needs assessment-type content to the overall vulnerability assessment. Drive-time analyses were then conducted to estimate the proportion of a jurisdiction with access to the specific service type. [8,9]
A final risk and resource map could then be produced showing the intersection and availability of relevant community resource locations with the highest-risk communities for each indicator as well as overall vulnerability groups/ranks.
Combining GIS, spatial epidemiologic, and statistical modeling analyses allows for a more comprehensive review of the spatial pattern of risk, exploration of correlation, and the potential alignment of community health assets to help highlight the communities that face the highest risk and that may require additional resources.
For more spatial epidemiology resources, please access the CSTE online training course: “GIS and Spatial Analysis for Hepatitis C Virus Surveillance, Vulnerability Assessment, and Intervention Planning”.
Oregon Vulnerability Assessment Project
Information provided by Pickle, 2019. Viral Hepatitis Program Acute and Communicable Diseases.
Oregon’s County-Level Jurisdiction Vulnerability Assessment applied spatial epidemiology using a variety of choropleth map approaches. Oregon used multiple methodological approaches beginning with a high number of key indicator variables that were reduced using backward stepwise regression modelling until only significantly associated variables were included.
Illinois Vulnerability Assessment Project
Information provided by Cara Bergo, Maternal Mortality Epidemiologist, 2019.
Illinois undertook their opioid-related vulnerability assessment to inform work at the state level to conduct prevention activities, such as working with local health departments to develop jurisdictional response plans. The Illinois team leveraged national (e.g., Census) and local data sources (e.g., NNDSS; vital records) to derive 30 independent variables at the ZIP code level to test for association with the outcome of interest: HCV infections in individuals younger than age 40; combining 2017-2018 data.