COVID-19 Holiday Surge

Copyright (c) 2021 D.S.Dixon
Data from the New York Times database.

One way to look at at the pace of the COVID-19 pandemic is in terms of the rate of change. If the rate of change is positive, the number of cases is increasing, and that’s bad. If the rate of change is decreasing, that’s better. But it’s not good until the rate of change is negative. That is, fewer cases each day.

The plot above shows the rate of change as a daily growth rate: the fractional change each day. Multiplied by 100 it’s a percent change each day. Since June that rate, for the U.S., has been between 1% per day and 2% per day. That is, one to two percent more people infected each day. That’s not good. If it goes on long enough at that rate, everyone gets infected, though that’s not going to happen because some people are immune for one reason or another.

You can find more plots, including individual state plots, on my website. The plot above just focuses on the period between 7 November 2020 and 7 January 2021. The thicker dashed line is the daily growth rate in total U.S. cases. Each thinner line is a U.S. State, the District of Columbia, Guam, Northern Mariana Islands, Puerto Rico, or Virgin Islands.

While the number of cases has been growing between one and two percent on average over this time, there are clearly three different trends here. One is the surge from 7 November to 2 December, labeled Halloween above, the second is the surge from 2 December to 30 December, labeled Thanksgiving, and the third is just starting on 30 December 2020.

I will be adding additional analysis on my website, but there are at least two things to take away from this snapshot here. One is that many states clearly participated in the surges shown, some much more than others. The other takeaway is that these surges run for around 30 days, starting about a week after a major holiday.

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