Introduction

The severe acute respiratory syndrome corona- virus-­2 (SARS-CoV-2) was identi ed in Wuhan City, Hubei Province, China in December 2019 and spread rapidly via human-to-human contact starting in 2020, with the World Health Organization (WHO) classifying SARS-CoV-2 infection and its resulting illness, coronavirus disease 2019 (COVID-19), as a global pandemic in March 2020. This highly transmissible virus led to high hospitalization rates throughout the world, with illness severity requiring hospitalization in up to 20% of those infected in the initial phase of the pandemic [1]. Cultural and geographic differences in practice, resources, comorbidities, and populations lead to wide variations in the level of care provided and patient outcomes. For example, in the initial hospitalized cohorts in China up to 26% required an intensive care unit (ICU) admission [2] but in the second year of the pandemic, less than 10% required intensive care due to better understanding, differing strains, treatments, and vaccinations. Global mortality in the rst 2 months of the pandemic was approximately 3.4% worldwide, with a high degree of variation by country and region [3].

E. S. Malsin (*) · A. C. Argento

Department of Medicine, Northwestern Memorial Hospital/Northwestern University, Chicago, IL, USA e-mail: elizabeth.malsin@nm.org; aargent1@jhu.edu

Though mortality rates decreased as the pandemic continued, the high transmissibility led to large portions of the global population becoming infected, again with high degree of variation at regional and national levels. At the time of this writing, approximately six million people worldwide have died from COVID-19 [4], though many experts think this an underestimate of the toll.

SARS-CoV-2 is a beta-coronavirus similar to the virus causing the original SARS epidemic in 2003. It has an incubation period of 14 days, with most symptoms beginning 4–5 days post-­ exposure [5, 6]. SARS-CoV-2 is usually transmitted via respiratory droplets, which are inhaled or deposited on mucous membranes, and do not usually travel more than 6 ft. Inhalation of contaminated aerosols is also a potential transmission route. Fever, fatigue, cough, and dyspnea are the most common presenting symptoms, though COVID-19 symptoms have proven highly variable. Asymptomatic transmission is common, and dependent on strain variant, with more recent strains such as Omicron having high transmissibility and low mortality. Comorbidities including obesity, diabetes mellitus, immunocompromised state, hypertension, and heart disease increase the likelihood of symptoms, hospitalization, and mortality, as does older age [5].

In the initial years of the pandemic, with growing understanding of SARS-CoV-2 and COVID 19 as well as the emergence of vaccinations, diver-