Monthly excess mortality across counties in the United States during the Covid-19 pandemic, March 2020 to February 2022

Excess mortality is the difference between expected and observed mortality in a given period and has emerged as a leading measure of the overall impact of the Covid-19 pandemic that is not biased by differences in testing or cause-of-death assignment. Spatially and temporally granular estimates of excess mortality are needed to understand which areas have been most impacted by the pandemic, evaluate exacerbating and mitigating factors, and inform response efforts, including allocating resources to affected communities. We estimated all-cause excess mortality for the United States from March 2020 through February 2022 by county and month using a Bayesian hierarchical model trained on data from 2015 to 2019. An estimated 1,159,580 excess deaths occurred during the first two years of the pandemic (first: 620,872; second: 538,708). Overall, excess mortality decreased in large metropolitan counties, but increased in nonmetro counties, between the first and second years of the pandemic. Despite the initial concentration of mortality in large metropolitan Northeast counties, beginning in February 2021, nonmetro South counties had the highest cumulative relative excess mortality. These results highlight the need for investments in rural health as the pandemic’s disproportionate impact on rural areas continues to grow. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The authors gratefully acknowledge financial support from the Robert Wood Johnson Foundation (77521), the National Institute on Aging (R01-AG060115-04 and R01-AG060115-04S1), the W.K. Kellogg Foundation, the Boston University Center for Emerging Infectious Diseases Policy and Research, and the Agency for Healthcare Research and Quality (T32HS013853). The content is solely the responsibility of the authors and does not necessarily represent the official views of the study sponsors. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Data used in the study are publicly available from the US Centers for Disease Control and Prevention and US Census Bureau. Additional details about the data and programming code for replication can be accessed at the linked GitHub repository: [https://github.com/The-Uncounted-Lab/county\_month\_excess\_mortality\_2020-2022][1] I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Data used in the study are publicly available from the US Centers for Disease Control and Prevention and US Census Bureau. Additional details about the data and programming code for replication can be accessed at the linked GitHub repository: [https://github.com/The-Uncounted-Lab/county\_month\_excess\_mortality\_2020-2022][1] [https://github.com/The-Uncounted-Lab/county\_month\_excess\_mortality\_2020-2022][1] [https://mu0brt-zhenwei-zhou.shinyapps.io/county\_ex\_app/][2] [1]: https://github.com/The-Uncounted-Lab/county_month_excess_mortality_2020-2022 [2]: https://mu0brt-zhenwei-zhou.shinyapps.io/county_ex_app/