US Trend Forecasting

I’ve described that it takes at least three weeks for changes in policy to begin to show up in the data related to COVID-19. Using that rationale, I’ve also indicated that the impacts of stay at home orders would begin having impact between April 12th and May 3rd. I have also projected that relaxing these restriction would start to show up in the data for most states between May 15th and the end of June. I did this so people could not accuse me of data mining retrospectively so I could have a prospective look at my hypothesis. We have reached that date for these states:

 North Dakota
 Rhode Island
 South Carolina
 West Virginia

A graph of the US data since March 15th can provide some insights. Cases are the bar graphs and use the left axis for the scale, deaths are along the red line and uses the right axis for scale. Splitting cases and deaths onto different vertical scales makes it easier to see them in comparison to each other.

First, I think it’s worth noting that deaths clearly follow the case trend, but with a delay of about a week.

I’ve broken the data into three sections each with a representative trend line for that period, the first based on the emergence of the pandemic and exponential growth.

The second section projects start of impact by stay at home orders in most states, which is represented by the green area over the dates. I’ve also included the following 11 days as part of the benefit of that period, although it likely extends even longer than that.

The orange section is the start of when I expected to see impacts from the relaxing of stay at home orders. Each state did this a little bit differently, but it had been my best effort to project forward from whatever language was used by a given state.

The dark straight trend lines for the cases in each section are what I’m most focused on. It’s clear we had rapid growth through the beginning of April and that we succeeded at flattening the curve as indicated by the second trend line.

While a subtle change, the third trend line is concerning. For those with a mathematical interest, the slope of the benefit of the stay at home section is -216.56. The slope of the line for the resurgence section is -128 currently. The important thing is that it has changed that much with only about 1/2 of the states starting to see the impact of those changes, and 11 of them in the last 8 days, so this is just the start of the change that is coming.

I accept that some of the increased case count is due to more testing. However, I am sticking to my initial estimate of the middle of June to start seeing a rapid climb in cases again followed by quickly overwhelming our ICUs and eventually our hospital beds and morgues.


One response to “US Trend Forecasting

  1. Pingback: Slopes by State | IP/EM/Safety

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