Incidence, clinical outcomes, and transmission dynamics of hospitalized 2019 coronavirus disease among 9,596,321 individuals residing in California and Washington, United States: a prospective cohort study

Joseph A Lewnard; Vincent X Liu; Michael L Jackson; Mark A Schmidt; Britta L Jewell; Jean P Flores; Chris Jentz; Graham R Northrup; Ayesha Mahmud; Arthur L Reingold; Maya Petersen; Nicholas P Jewell; Scott Young; Jim Bellows

Months after its emergence in central China, the novel coronavirus SARS-CoV-2 has become pandemic, with cases of 2019 coronavirus disease reported in nearly all countries. 1 A total of 525,704 cases and 20,486 deaths were reported in the United States as of April 12, 2020 , representing the greatest total of any country. 2 Surges in COVID-19 cases have overwhelmed the capacity of hospital and healthcare systems in certain regions of the US, mirroring significant disruption witnessed in other countries. [3] [4] [5] However, the epidemiology of COVID-19 in the United States remains poorly described, including clinical parameters of disease progression, the risk of intensive care unit (ICU) admission and death by patient age and sex, and the duration of hospital stay. As such, efforts to forecast trajectories of the epidemic to guide planning and response in the United States and other high-income settings have relied almost entirely on data from China to inform these parameters, 6 which may not adequately reflect clinical circumstances elsewhere.