Abstract
COVID-19 case rates in the USA wax and wane in wave-like patterns over time, but the spatial patterns of these temporal epidemic waves have not been well characterized. By analyzing state- and county-level COVID-19 case rate data for spatiotemporal decomposition modes and oscillatory patterns, we demonstrate that the transmission dynamics of COVID-19 feature recurrent spatiotemporal patterns. In addition to the well-recognized national level annual mid-winter surges, we demonstrate a prominent but previously unrecognized six-month north-south oscillation in the eastern USA (Eastern US COVID Oscillator – EUCO) that gives rise to regional sub-epidemics and travelling epidemic waves. We also demonstrate a second less prominent pattern that oscillates east-west in the northern USA (Northern US COVID Oscillator – NUCO). The drivers of these newly recognized oscillatory epidemic patterns remain to be elucidated. Since the first documented case of SARS-CoV-2 in the USA in January of 2020, the virus has caused nearly 100 million reported infections and more than 1 million deaths.1 COVID-19 incidences have waxed and waned several times a year, with month-to-month variations in intensity in different regions of the country.1 The spatiotemporal granularity of available COVID-19 data in the USA provides an unprecedented opportunity to investigate detailed epidemiological dynamics of an infectious disease. In this study, we examine this spatiotemporal data in the USA to reveal patterns that can aid in the understanding COVID-19 waves and their oscillatory behavior in the United States.