Most States Shifting to Linear Growth

Sorry I didn't post yesterday, but I needed a day off. Across the board, case counts came in lower than would be otherwise expected, but we're learning to expect that on Sundays.

Today, Spain's cases are looking especially good, with only about 3/4 of the new cases that my models predict, even accounting for Mondays being lower on average. Also, Spain, Italy, and Germany are all looking a little better than expected. Yesterday, Switzerland saw the total number of active cases grow by about 4%, but that's not enough to counteract Saturday's amazing drop of -5%. Today, they posted another encouraging drop of 8%, due to a slightly lower than average set of new cases combined with a large number of reported recoveries. France, and the Netherlands are all very well in line with the linear model. The UK, US, and Canada are all still not on the linear growth model yet, but appear to be slowly heading in that direction, as they come in under the exponential growth curve. If they continue at this rate, I expect Canada and UK to be linear within a week, and the US shortly after, but there are a lot of heterogeneous components to that actually happening. In the Mideast, Iran has fewer confirmed active cases, but that all comes from an increase in resolved cases, as new cases remains constant. Israel is doing slightly better today, and Turkey is still on track.

In the United States, most of the states with a large number of infections are switching over to the linear growth model. Maryland is still exponential, while Pennsylvania and Texas are still in a transition model. Louisiana and Tennessee are unpredictable right now, so no telling what will happen there, yet. Arizona and Alabama look like they are continuing with exponential growth. Connecticut had a bad day, with 1214 new confirmed cases (22% growth), but that looks like an outlier. The states with under 2000 cases are mostly unpredictable right now, with especially erratic behavior out of the Midwest. Many of these areas have limited resources and logistics for testing and reporting, contributing to the noise. Taken as a group, however, these states are showing distinct exponential growth.

I am still searching for an explanation to the linear growth effect we are seeing. While there are plenty of epidemiology papers describing late-stage linear (or at least sub-exponential) growth, these are all saturation effects that do not accurately describe the scale or duration of what we are observing. Admittedly, the stay-at-home behavior we are using to fight this epidemic is not something we have seen at this scale before, either, so I'm not too surprised. However, I am still hopeful that we can better understand the cause and model the core behavior so that we plan a better exit out of this situation we have found ourselves in, without having to wait for vaccines or cures for something as hard to defeat as the common cold.