Thanks to some fantastic data available on github here we can now repeat the same analysis for the US to see what is actually taking place and why the new case rate is stubbornly holding at about 30,000 new cases per day.
I found some very interesting charts on the New York Times website, which had neatly segmented each state into groups based on growth, however the accompanying charts were difficult to read and differently scaled which made comparison difficult. So I've gone back to my growth dynamic analysis to obtain the result below:
Here we see the position of each state in terms of week on week growth rate for new cases (note the reversed x-axis), the new cases per 100K population on the y-axis and the bubble size representing the number of new cases in the latest week.
The blue arrow shows a typical trajectory over time, although the actual shape and order of magnitude will vary on a case by case basis.
Overall the situation if quite balanced - some states still seeing a growth in cases, some flattening and some with declining rates of new cases. However the circles above will shift to the right in the coming weeks which will reduce the rate of new cases significantly and an overall decline in the national figures will follow quickly.
Some key turning points include several areas with declining rates of new cases, but on a high basis of infection (large circles to the upper right). These include New York, New Jersey and Massachusetts. These areas will no doubt have experienced extremely high loading on the local healthcare resources, but new cases are starting to decline, which will help reducing loading going forward.
By comparison California is seeing declining rates of new cases, but never peaked as high as the first group and Pennsylvania is just hitting peak now, but at a lower level than the first group. (Large circles, but lower on the y-axis).
Areas of concern are those states towards the upper left of the chart. Illinois has both high levels of infection, a high number of new cases and is still growing, so healthcare loading will be high and cases numbers will be off-setting the decreases seen elsewhere. However, based on analyses of other areas, cases may well peak here in the next few weeks.
Maryland, Iowa an Delaware are also still growing in areas with high infection rates, but are smaller numbers, so hopefully these areas will slow down too.
Nebraska is a potential concern, with high week on week growth of 77%, which has the potential to grow exponentially in the short term and could see some of the highest levels of new cases per 100K population recorded if the current trends continue.
Also of note here is Minnesota, new cases are growing rapidly here but on a relatively small base at the moment. Hopefully local measures will be able to reduce the increase in new cases and avoid the state following the full lifecycle shown by the blue line.
For those of you into your figures, please find the key figures from the diagram above in the tables below:
Thanks to the quality of the data for the US, it is easy to map the data (as below) and it is noticeable that the new cases (even when indexed to population) are clearly clustered to the East Coast of the US (see map below), with the other three larger column of note being Nebraska, Iowa and Illinois, which fits with the first chart perfectly.
To help visualise the spread of new cases in the US, I've creating the following animation that shows cumulative cases over time. I've omitted data before March 2020 for the sake of time and clarity.
Unfortunately the high values in New York and New Jersey make it difficult to see many of the more subtle patterns in the data, so please find the version below with New York, New Jersey and small values excluded, which gives more insight into some of the other centres of infection in the US.
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