Article Summary: A second wave of COVID-19 in Chicago USA: A case for urgent action

Arling, G., Blaser, M., Cailas, M., Canar, J., Cooper, B., Geraci, P., Osiecki, K., & Sambanis, A. (2020). A second wave of COVID-19 in Cook County: What lessons can be applied?. Online Journal of Public Health Informatics, 12(2).

During the current public health crisis in the US, information on COVID-19 mortality is typically reported for the overall population of a city or state, at single time points, and without regard to residential location, particularly individual households compared to long-term care facilities or other congregate settings. In our study of COVID-19 mortality in Cook County IL (Chicago and suburbs), we examined patterns in COVID-19 mortality over time at the neighborhood level (postal Zip codes) in households and in nursing homes and other long-term care facilities (LTCFs).

Setting, Data and Methods

Cook County is an excellent setting for this study because of its large size, densely populated areas, racial and socio-economic diversity, and multiplicity of neighborhoods and LTCFs spread across a large geographical area. Chicago and the surrounding suburbs experienced a major wave of COVID-19 in the Spring with a lull during the summer and early fall. Now the metropolitan area appears to be entering a 2nd major wave. The major data source for this study is the Medical Examiner (ME) Case Archive of COVID-19-related Deaths. This archive is organized in a searchable online database format and contains information about deaths that occurred in Cook County at an address level. Another source of data was the Centers for Medicare and Medicaid Services (CMS), which regulates nursing homes and maintains a database of LTCF related deaths across the United States. Data preparation and statistical analysis were performed with the IBM® SPSS® Modeller 18.2.1. Geocoding, data projections, geospatial data integration, mapping, and initial spatial analysis were performed using ESRI’s ArcGIS Pro.  


  • Household (non-LTCF) COVID-19 mortality in Cook County is accelerating in a manner similar to the early phase of 1st wave in the Spring. LTCF mortality is displaying the same pattern, except with 2-3 week lag, which is likely due to the time for COVID-19 to be transmitted from community to LTCFs. During the 1st wave, LTCF deaths peaked at the alarming rate of 40 deaths per day. As of November 25, the death toll was concentrated in a relatively small number of the county’s 200+ facilities: 52% of LTCF deaths were located in 18 LTCFs in 10 ZIP codes. A month ago COVID-19 related deaths were 2 per day, currently deaths are close to 10 per day.
  • Three neighborhood (zip code) characteristics are related to household COVID-19 mortality: high percentage of Black, Hispanic or other minority group residents; high population density (persons/ square mile); and low socio-economic status. These findings are consistent with general population patterns in other studies; however, we are able to pinpoint patterns at the neighborhood level.
  • Transmission of COVID-19 into LTCFs did not appear to be linked to incidence of COVID-19 in the immediate neighborhood. The rate of COVID-19 mortality in LTCFs was unrelated to the rate of community mortality in the same zip code. In analysis of a subset of nursing home data, we found parallel patterns over time in incidence of COVID-19 cases among nursing facility staff and residents. These findings raise the possibility, suggested by other researchers, that transmission may be occurring through LTCF staff living in the wider community, perhaps in high-risk neighborhoods in other parts of the county.
  • Another possible contributor to spread of COVID-19 is transfer of individuals between acute care hospitals and LTCFs. Cook County nursing facilities had over 190 weekly COVID-19 admissions from the hospital in June, a drop in admissions to 50/week from July – October, and then a sharp upward trend to 150 admissions/week in November. The increase may portend a rise in COVID-19 deaths among nursing facility residents.


Findings from our research point to the urgency of immediate action to prevent an acceleration of COVID-19 cases and consequent deaths both in LTCFs and high-risk neighborhoods, especially neighborhoods with concentrations of minority group residents. Moreover, distribution of vaccines should be prioritized not only to nursing home residents and staff, as currently planned, but also residents of high-risk neighborhoods.

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