Study population and setting
The study objective was to estimate the burden of hospitalization and ICU admissions for COVID-19 across the US in 3,142 counties as identified in the 2010 US census. The study used data from the 2018 American Community Survey to estimate the age-specific demographic distribution in each county, and the American Hospital Association 2018 annual survey to estimate the number of hospital beds and ICUs available in a given county. Counties without beds or ICUs were then distributed to the nearby counties with greater capacity. The study used a susceptible-exposed-infected-recovered (SEIR) transmission model, and assumed a constant population in the counties included. Authors compared outcomes from two models with varying assumptions about intensity of transmission: 1) a pessimistic transmission model which assumed the reproductive number was 5; 2) an optimistic model in which it was assumed to be 2.
Summary of Main Findings
The model estimated 315 counties at or above the 90th percentile of per-capita hospitalization in the optimistic scenario, and 308 were also at or above the 90th percentile in the pessimistic scenario. Counties with relatively larger populations over the age of 60 were most likely to experience more hospitalizations from COVID-19. The counties with the greatest estimated burden were, for the most part, far from urban centers. In assessing the cumulative burden of hospitalizations, 247 counties were at or above the 90th percentile in both transmission scenarios for cumulative hospitalization per bed and were scattered across the US, and were mostly from the west and the northern midwest. 136 counties were at or above the 90th percentile for ICU admission per bed to estimate ICU utilization in comparison to healthcare system capacity, though these counties were not statistically more likely to be rural.
The study used two nationwide surveys in order to inform the model for each county, and was able to assume cases in areas with reduced hospital and ICU capacity sought care in nearby counties with capacity, as might happen in a real-world scenario. Many of the study’s results regarding the highest burden areas were robust to both optimistic and pessimistic transmission scenarios. They estimated cumulative hospitalization/ICU utilization in order to circumvent issues of temporality and inaccuracies in estimating a specific transmission peak.
The study made numerous assumptions, which was necessary for their models but may reduce the applicability of the findings. For instance, their optimistic reproductive number of 2 does not take into account interventions such as shutdowns and stay-at-home orders, that may further reduce the reproductive number. They also assumed 20% of the population in each county eventually becomes infected, which may not be a reasonable assumption, given areas that are urban are likely to experience higher transmission than very rural areas with lower contact between individuals. Finally, the study used data on hospital and ICU bed capacity from 2018, which does not account for field hospitals or other stockpiling of ventilators and other equipment to increase hospital capacity which may occur in response to the pandemic.
This study estimated the cumulative hospitalization and ICU-related health system burden due to COVID-19 across the United States, and demonstrated that many rural counties will likely be unable to cope with the demand for hospitalizations without efforts to increase capacity, which has important policy implications for resource allocation and planning during the pandemic.
This review was posted on: 1 August 2020