COVID-19 Progression Timeline and Effectiveness of Response-to-Spread Interventions across the United States

Pai Liu; Payton Beeler; Rajan K Chakrabarty

Forecasts have been performed in the timeframe between March 2 and 16. For each forecast, the SEIR model was initialized with the daily confirmed active cases of COVID-19 in the US (Refer to Table S2 in Supplementary materials (19) ), which were acquired from a web-based dashboard for real-time epidemic tracking published by Johns Hopkins University (8) . The matrices of (hereafter ) and were calculated using the latest monthly aviation data (between September 2018 and August 2019) released by the United States Bureau of Transportation Statistics (23) (The calculation of and is detailed in Supplementary Materials (19) ). The state-wise population was acquired from database of United States Census Bureau (24). The 0 , , and of COVID-19 were assumed to be 2.68, 6 days, and 2.4 days, respectively, per the values recommended in Ref. (2) . Figure 2 shows forecast of SEIR model initialized on March 16 under a status quo condition. Panel (a) shows the dynamics of COVID-19 spread in the US, highlighting the temporal evolution of infected population ( ) state-by-state sorted by the earliness of the arrival of local epidemic peak. Panel (b) maps the spread pattern of COVID-19 by showing a time series of continental US map wherein each state is colored according to the local infected fraction. Among the earliest outbreaks along the pacific west region, epidemics in Washington will reach a local peak by May 21. Immediately followed is the state of New York, wherein a local epidemic peak is expected to arrive by May 25. Alaska will experience a rapid increase in local infected fraction, which will peak around May 29, because of its frequent air traffic commuting from and to Washington. Similar trend is observed for Hawaii, where the local epidemic is estimated to peak on June 3, under the influence of high passenger flux emanating from California whose local epidemic peak will arrive around June 1. The local epidemics in Massachusetts, Washington DC, Colorado, and New Jersey will peak by the end of May, which is followed by Illinois, Georgia, and Florida, where the local epidemic peaks are expected to arrive by early June. The majority of states will experience epidemic peaks during the first week of June. The daily active COVID-19 cases at the epidemic peak (hereafter, epidemic peak magnitude), is uniform across each state with a median value ≈ 7.59% of the state-wise population. The national epidemic peak is estimated to arrive on June 3, with an daily active cases ≈ 7.16% of total US population.