On December 31, 2021, the Illinois Department of Public Health (IDPH) reported a cummulative total of 3031 positive COVID-19 tests in Warren County. This post will we revisit the first 1000 cases and take a look at how they compare to this most recent 1000 caces. This analysis looks only at postive tests, at cases. I do not have good data for looking at severity of cases beyond the extreme case of death due to complications from COVID. What we’re concerned with here is how many people are getting COVID and what we know about the ages of these people.
The Shape of Things
Let’s begin by looking at the day-to-day numbers since the beginning. The IDPH reported the first COVID case in the county on April 11, 2020. Since that time we’ve seen three major surges come and go. First was the initial surge of 2020 that seems to have been largely driven by cases coming into and out of the local pork processing plant. Following that surge was the Fall 2020 to Winter 2021 surge which was, until recently, the high-point for the virus locally and national. Both of these surges are presumed to have been the original strain of the virus. By late summer of 2021 we started to see the Delta variant surge. By this time we had vaccines available for everyone aged 12 years and up and it’s likely that this helped keep the Delta surge down relative to the Fall 2020 surge. By October 2021, the delta surge had largely subsided but the drop in cases seems to have stalled out at a higher levels than previous cases. Put another way, we never really flattened the curve after the Delta surge and so we rolled into what is presumably an Omicron variant surge with a moderately high to high level of spread in the community. By late November 2021, the Omicron surge seems to have begun in ernest and we still continue to see an upward trajectory that inclues new daily and weekly postive case records coming out of the IDPH. We can see all of this play out in the blue bars on the following graph. The dark blue line is the seven day average for new cases, which does a pretty good job of smoothing out the overall trajectory of the pandemic.
The three boxes on the graph break the pandemic into roughly 1000 case increments. We crossed the 1000 case threshold on November 24, 2020, right around the peak of the Fall 2020 surge. The 2000 case threshold was crossed on August 29, 2021, at the start of the Delta variant surge. As stated above, the 3000 case threshold was crossed on the last day of 2021, and coincides with the start of the Omicron surge. What’s clear from just looking at the boxes is this most recently batch of 1000 cases came much quicker than the previous two batches. Below you can see a table listing the basic stats for each of these boxes: the dates they cover, actual number of total cases reported on those dates (cummulative total), the number of cases reported within the box (period total), and the number of days spanned by the box (time to accumulate).
Finally, going back to the first graph, you’ll see I included the six days of 2022 that were available at the time of writing this post. Those six days account for 150 new cases. This is at historical highs and is a sign that our next 1000 cases could come even faster than this last 1000 if this surge doesn’t turn around quickly.
Who’s Getting Sick?
It’s not just time and variants that make these three blocks of the pandemic different. The age demographics of each block changes as well. Here you can see the age demographics of each of the previously identified blocks.
Early in the pandemic we saw cases concentrated in the older age groups, but as time has gone on the cases have started to shift into younger demographics. The most recent 1000 cases are strongly concentrated in the under 20 age group. There are a lot of potential reasons for this shift and these data alone do not really let us determine a cause for the shift. What we can do is look back a bit at how we were handling the pandemic and consider ways that our protective measures might correolate with these shifts.
Early stages of the pandemic were marked by extreme lockdown. School-aged kids were, for the most part, at home and a great number of jobs went remote. The groups most are risk were those working essential jobs or jobs that could not possibly be done remotely. It makes sense that this would concentrate cases in the 30-60 age ranges. By the second 1000 cases we were putting kids back in school and starting more agressive testing practices for student athelets. This would not only incrase the risk for young people but increase the likelihood that we’d catch mild and asyptomatic cases in that population. In the meantime, vaccines were rolling out for adults but were not avaiable for kids 12 and up until May 2021. Combine all of this with the end of lockdowns and it’s not suprising that the second 1000 cases are more evenly distributed across the different age demographics.
What clearly stands out about the demographics of the 2000 to 3000 case block is how heavily it’s weighted towards the under 20 demographic. The start of this block was during the Delta surge. Vaccines were available for everyone 12 and up. Boosters started rolling out, and, by the end of the block, were made available to all adults. It wasn’t until nearly a month ago, the tail end of the block, that vaccines were first made available for everyone 5 and up. So, from the vaccine perspective, this shift towards youth cases isn’t terribly surprising. The 20 and under demographic had the least amount of available protection from the virus. In the face of their disporportionate risk of infection, we moved away from lockdowns while attempting to maintain some protective measures like masking, distancing when possible, and some amount of proactive testing. However, these measures are not practiced uniformly in the community. I see as many or more unmaked people in stores as I do masked and large gatherings that lack appritiable social distancing have certainly been taking place even though the the lowest spread of this most recent block of 1000 cases was not what health officials consider low risk. Finally, while vaccines are avaiable for most of the county, less than 50% of the population has opted to get vaccinated. All told, it certainly seems like we’ve maintained a thin saftey net over the course of this most recent block of 1000 cases and as a result have seen the virus spread within the least protected parts of the community.