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Illinois COVID-19 Trend Tracking – are case counts going up or down?

6/24/20 – The 7 day average was pretty flat this week, rather than trending down as it had been.  Also, today the case count was higher than would have been expected, which is a worrisome sign.

I created the above graph because Illinois cases are tracked weirdly, with low cases recorded on the weekends and those extra cases reported during the week.  In order to get a better sense of the trend, I’ve done a 7 day moving average, so it takes into account the entire week’s cases.  With July 4 coming up, I’m guessing cases will not get accurately reported on the Friday holiday (which happened on Memorial Day), so I also am recording a 14 day moving average.

Unfortunately, it still can take some time to notice a change in trends, especially during holiday weeks.  The new cases should definitely be lower than the same day of the week, one week prior.  Not only should the case count be lower this week than it was the same day last week, it should be down at least a specific amount, based on the current rate that cases are supposed to be declining.  If the cases are not going down as quickly as expected, it may signal that another spike is coming.  Unfortunately, calculating that expected rate of change is more complicated than what I have time to figure out for right now, as the rate of change will decline as the case counts go down (causing the classic “bell” curve or Gaussian curve).  Using the simple method of just comparing to the previous week will give us an indication that cases are going up, but it may take longer before we notice the trend has reversed.

I’m going to use this blog entry to keep track of my interpretations of the daily case counts in Illinois to try to indicate if another spike is coming.  Based on today’s numbers, I am concerned an increase in cases may be coming.  One day may be an anomaly, so I’ll be looking at patterns over several days.

June 24 – higher number of cases than I would have expected, perhaps signaling the downward trend in Illinois is ending

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