(Last updated on 2020-11-01 12:53:27. A version as of May 4th was published at Medium. For further data, including states ranked by the latest 7-day average of new cases per popoulation, please see this.)
When to reopen? That is the key question that states are asking themselves seven weeks after the White House released its guidelines, “15 Days to Slow the Spread”, on March 16.
More recently, the White House has provided criteria on when to reopen, including “Downward trajectory of documented cases within a 14-day period.” While a “downward trajectory” can be confirmed numerically, it’s helpful for those of us who are more visually oriented to see what these curves look like. And for those of us in states that have not yet reopened - and who may be looking on with some envy at those that have - it’s natural to want to know how our situations compare and when our state may be ready.
(Note: As of June 27th, the example state was changed from Montana to Vermont. Montana is experiencing a large increase in new cases, and does not have a typical complete first wave curve any more. See below.)
Let’s use Vermont as an example. Daily new cases (the black line, smoothed over 7 days) reached a peak at the beginning of April and have been declining fairly consistently ever since. Total cases (the grey bars) leveled out at the end of April. Vermont clearly meets the White House criterion for “downward trajectory” - and did so by the end of April (Vermont started reopening on April 27th).
Vermont also helps us understand what a complete first wave of infection looks like. There are three distinct phases, that we are calling acceleration, moderation and stabilization:
Phase 1 - Acceleration (shaded red): Starts when total cases (gray bars below) exceeds 1 per 100,000 population and ends when daily new cases (black line below) reaches a peak (about 41 in total - up from about 3 at the start). In this phase, new and total cases are increasing rapidly, and often exponentially, especially at the start.
Phase 2 - Moderation (shaded orange): Starts at the peak and ends when the number of daily new cases has declined to where it was at the start of phase 1 (3 cases in total or 0.5 per 100,000 in Vermont). During this phase, total cases are still going up, but less quickly, and daily new cases are declining.
Phase 3 - Stabilization (shaded yellow): During this phase, new and total cases are essentially flat. Daily new cases are low and manageable, and total cases are growing very slowly. The epidemic is “under control” and if it hasn’t already, the state can start reopening with appropriate safeguards in place.
The daily new cases, however, has fluctuated in the state, and it is important to keep the daily new cases under or close to the threshold that triggered phase 1 (the dotteed line below).
Hover over the figure to see values and more options.
Now let’s turn to the other states. While each state has its own unique circumstances when it comes to its politics, economy, etc., certain patterns start to emerge when comparing their first wave curves. We’ve divided them into four categories depending on where they are on their curves as of 2020-11-01.
As of 2020-11-01, 0 state is in the stabilization phase. Previously, four states (Alaska, Hawaii, Montana, and Vermont) were once in this phase, but the new number of cases has either fluctuated (e.g., Vermont) or increased (e.g., Alaska) in all of them.
2 states are near the stabilization phase, with daily new cases down more than 75% from their peak levels. They can start reopening as long as they meet the other White House criteria and have appropriate safeguards in place.
Note: The x-axis is days from the first day of phase 1. The y-axis is daily new cases per 100,000 population (necessary for comparing big and small states). The light gray box shows a range between the baseline, at which the first wave started, and 75% down from the peak in each state.
Hover over the figures to see the underlying data.
8 states are in the late moderation phase, with daily new cases down 50-75% from their peaks. They are on a trajectory to reach phase 3 as long as they don’t relax their current safeguards, and can start actively planning for reopening.
Note: The x-axis is days from the first day of phase 1. The y-axis is daily new cases per 100,000 population (necessary for comparing big and small states). The light gray box shows a range between 75% and 50% down from the peak in each state.
Hover over the figures to see the underlying data.
9 states are in the early moderation phase, with daily new cases down 25-50% from their peaks. They have made progress, but should not relax their current safeguards. They can start planning for reopening, but reducing new cases remains their top priority.
Note: The x-axis is days from the first day of phase 1. The y-axis is daily new cases per 100,000 population (necessary for comparing big and small states). The light gray box shows a range between 50% and 25% down from the peak in each state.
Hover over the figures to see the underlying data.
Unfortunately, 32 states have not yet reached or are still close to their peaks, with daily new cases either increasing, stalled, or down less than 25% from their peaks. Rather than relaxing their safeguards, they should instead be considering strengthening them.
Note: The x-axis is days from the first day of phase 1. The y-axis is daily new cases per 100,000 population (necessary for comparing big and small states). The light gray box shows a range between the peak and 25% down from the peak in each state.
Hover over the figures to see the underlying data.
Clearly, some states are already at a stage to consider reopening now or in the near future, at least from an epidemiological point of view. The majority of states, however, still need to prioritize slowing new cases and controlling the epidemic.
All COVID-19 data (i.e., cumulative confirmed cases and deaths by day) come from JHU/CSSE, accessed on 2020-11-01. All data on state population come from US Census Bureau, accessed on March 29, 2020.
For those interested in the methods and more data by state, please see this.
For those interested in the US curve, compared to other countries, please see this.
See GitHub for data, code, and more information. For typos, errors, and questions, contact me at www.isquared.global.
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