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A Spatio-Demographic Perspective on the Role of Social Determinants of Health and Chronic Disease in Determining a Population’s Vulnerability to COVID-19
ORIGINAL RESEARCH — Volume 19 — June 30, 2022
PEER REVIEWED
In Stage 1, confirmed cases were about 130 on every day. In Stage 2, confirmed cases exceeded 500 per day in the first half of the stage, and dropped to around 330 on subsequent days. In Stage 3, cases were all around 300. Stage 4 saw an abrupt increase in confirmed cases, exceeding 3,000 by early January 2021 and then decreasing to about 1,700 by early February. Finally, in Stage 5, case numbers fell sharply, from the high of about 1,700 in early February to about 250 by early April, when Stage 5 ended.
Figure 1.
Trends in confirmed cases of COVID-19 over time, San Diego County, California, March 31, 2020, to April 3, 2021. The graph illustrates how the number of county-wide confirmed cases varied during the study period. Observed confirmed case trends were used to define 5 pandemic stages: March 31, 2020, to June 24, 2020 (Stage 1, 85 days); June 25, 2020, to August 18, 2020 (Stage 2, 54 days); August 19, 2020, to October 31, 2020 (Stage 3, 73 days); November 1, 2020, to January 23, 2021 (Stage 4, 83 days); and January 24, 2021, to April 3, 2021 (Stage 5, 69 days).
The figure consists of 5 maps of San Diego County subregional areas (SRAs) shaded to illustrate the average daily COVID-19 case rate per 100,000 residents during each pandemic stage. During Stages 1 and 3, only SRAs along the county’s southern border had rates above 10 cases per 100,000 residents per day, ranging from zero to 20 to 30 per day. Elevated case rates also appeared in northwestern SRAs during Stages 2 and 5. Stage 4 had much higher case rates throughout the county than the other stages, with the highest rates in the south and northwest. Stage 4 rates ranged from 10 to 20 per 100,000 in 1 northwestern SRA to 70 to 80 per 100,000 in several other SRAs, reaching 119.01 in 1 southwestern SRA on the Mexican border. Rates declined throughout the county in Stage 5 and ranged from zero to 20 to 30 per 100,000.
Figure 2.
Spatial distribution of confirmed cases of COVID-19 by subregional area, San Diego County, California, March 31, 2020, to April 3, 2021. Maps show the spatial distribution of average daily COVID-19 case rates by subregional area for each of the 5 pandemic stages. Stages were determined by 7-day average case trends. All rates are per 100,000 residents.
Figure 3 is divided into 3 sections, A, B, and C. Each section consists of a series of 5 maps, one for each stage of the pandemic. Section A, the first map series, depicts the relationship between the age-adjusted hospitalization rate for hypertensive disease and the COVID-19 daily average stage case rates through layered 3-class quantile classification symbology. County subregional areas generally follow a high–high, low–low rate pattern, with exceptions in rural subregional areas to the north and east. Section B, the second map series, shows the local bivariate relationship between the age-adjusted hospitalization rate for hypertensive disease and the COVID-19 daily average stage case rates, which is predominantly linear in pandemic stage 1 but shifts to concave in the south by stage 5. Stage 3 does not have significant local bivariate relationships. Section C, the third map series, presents standard residuals for the geographically weighted regression models. In general, eastern subregional areas had COVID-19 rates lower than predicted and western subregional areas had COVID-19 rates that were either accurately predicted (standard deviation between −0.5 and 0.5) or higher than predicted.
Figure 3.
Bivariate visualizations of the age-adjusted hospitalization rate (independent) for hypertensive disease (hypertension, hypertensive heart disease, hypertensive chronic kidney disease, and hypertensive encephalopathy) and the daily average stage case rates (dependent) for COVID-19 in San Diego County subregional areas. Stages were determined by 7-day average case trends: Stage 1: March 31, 2020, to June 24, 2020; Stage 2: June 25, 2020, to August 18, 2020; Stage 3: August 19, 2020, to October 31, 2020; Stage 4: November 1, 2020, to January 23, 2021; and Stage 5: January 24, 2021, to April 3, 2021. Hospitalization rates for hypertensive disease (hypertension, hypertensive heart disease, hypertensive chronic kidney disease, and hypertensive encephalopathy) are for 2017 and consider the annual, age-adjusted rate per 100,000 residents. COVID-19 case rates consider the average daily rates per 100,000 residents for the stage. A. Layered quantile classification method for hypertensive disease hospitalization rates and the COVID-19 case rates. B. Type of local bivariate relationship for hypertensive disease hospitalization rates and COVID-19 case rates (rates not calculated for fewer than 5 events). C. Geographically weighted regression standardized residuals (prediction errors) as SDs for hypertensive disease hospitalization rates and COVID-19 case rates. Negative SD values indicate overpredicted COVID-19 case rates whereas positive SD values indicate underpredicted COVID-19 case rates.
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