The COVID Digest, 23Jul2021
Here we go, Georgia
Good evening! Let’s dig in to this week’s data for Georgia.
Cases rose this week by 78% this week compared to the previous week (when a +70% increase was observed). Hospitalizations were about the same as the previous week. ICU admissions decreased by 16% and deaths decreased 9.5%.
But these are just the cases we know about. If we look at what’s happening with test positivity, it’s clear that we are missing cases now and we’re missing more and more each day. So the 11,729 cases reported this week are likely an underestimate. For PCR testing, weekly test output increased 22% but the positivity rate rose 70% compared to the previous week and is now at 8%. For antigen testing, weekly test output rose 17% but positivity rose 56% compared to the previous week to 10.6%.
It’s harder to control disease when you can’t see how big the problem is. And with test positivity rising as it is, things are spiraling out of control. The delta variant is going to burn through the state, just as it has in Missouri, Arkansas, and Louisiana.
If we look at cases, we can see that case rate for the state has risen 324% since 01Jul. Rural counties have lower vaccination rates, and they have the highest case rate. But case rates are rising similarly for all other parts of Georgia.
The bad news is that we are just now starting to see the impacts of 4th of July gatherings and travel. Here’s why.
For those who were exposed on 4th of July, here’s the timeline for disease course and when we find out about cases. The timing of events is based on the median value (and range, if applicable) for each metric as determined by CDC. It takes about 6 days for a person to start experiencing symptoms. People often wait a couple days before seeking a test. And some people will have symptoms early on that hit them hard enough to send them to the emergency room - when they get a test for COVID-19. Most tests are turned around in 3 days or less now, according to the HHS Community Profile Reports. But when labs were stressed a year ago, it took up to 2 weeks for tests to come back. Cases are supposed to be reported within 24 hours, but delays happen, thus the dashed line to the right on test reporting. But we are right in the sweet spot of when the effects of 4th of July can be seen in the data.
Meanwhile, remember that each person who was exposed on 4th of July likely went on to expose other people too. So these timelines are happening for lots of people in a staggered fashion. So the original virus was estimated to have an R0 value of ~2.5. That means that in a never exposed population, for each person infected they would go on to infect an average of 2.5 people. The alpha variant from this spring was estimated to be ~60% higher than that, which might mean that the R0 value for alpha was about 4. The delta variant is estimated to be 60% more transmissible than the alpha variant. So that takes us to a possible R0 of 6. So instead of a single infected person infecting 2.5 other people, they might be infecting 6. If you take that through ten exposures…
Original: 2.5 -> 6.25……-> 9536 infected people
Alpha: 4 -> 16……-> 1,048,576 infected people
Delta: 6 -> 36……-> 60,466,176 infected people
Now, we don’t live in a never exposed population anymore - not with as many people who have been vaccinated and who have been infected. So we aren’t likely to see these numbers. But it’s a helpful thought experiment to put this down on paper so that we can see how much the situation can spiral out of control with higher transmissibility.
So who is getting sick? Let’s look at this week’s PCR cases by age. Note, this does not include antigen cases - for which we do not get demographic details from the Georgia Department of Public Health.
Cases rose this week for every age group and these are pretty dramatic increases. As we’ve seen in previous surges, things surge hardest and fastest among the 18-29 year olds.
As shown in the timeline above, cases and hospital admissions can rise together. The proportion of patients in the hospital who are there for COVID-19 continues to rise dramatically for the state (see below). But the number of new admissions this week were about the same as the previous week. What can explain this? The two things measure different things. New admissions are just that - new people being admitted as patients. Patient census is how many beds are occupied by COVID-19 patients. So if patient census is rising but new admissions are steady, this means that hospitals aren’t discharging people at the same rate that they’re admitting them. People who need a hospital bed for COVID-19 are having extended stays. As patient census (and beds occupied) rises, hospitals will have a harder time admitting new patients for anything - not just COVID-19. That’s what we’re seeing play out in other states.
The graph above is the state average. But if you dig into the regions, some are far worse than others. The scariest looking graph is for hospital region J (Savannah and coastal Georgia). We are seeing vertical growth of patients in the hospital.
The table on the right shows ICU bed usage and COVID-19 patient census in the second column. Today’s the first day since 09May that we’ve had a hospital region in the orange zone. And now hospital region M is orange. The entire state was in the green zone for this metric as recently as 09Jul. This kind of growth is not sustainable for hospitals.
Meanwhile, we tend to think of those in the hospital as those who might be older, weaker, or with underlying medical conditions. People might think that because they are young and healthy, that they’re invincible against this virus. But the people going into the hospital are younger than we saw in previous surges. There are as many 40-49 year olds in the hospital as 60-69 year olds. There are more 30-39 year olds in the hospital than those 80+.
Of course, children (especially those under age 12) have no opportunity to be vaccinated. Their best hope at protection is that the people around them are limiting transmission as much as possible through vaccination, masking, and social distancing. But unfortunately our communities are coming up short on that responsibility. Meanwhile, ER visits for children and young adults for COVID-19 are surging.
I’ve spoken before about how being deep in the data can be an emotional burden, remembering that each number is a person and a family. And in the past few months, I’ve tried hard to detach, imagining I’m tracking apples or butterflies, etc. But when I see a graph like the one above from Georgia DPH, I’m snapped back to the reality that in the next few weeks as schools reopen for in person learning with no vaccine requirements and no masks in some districts, these will be our kids in the data. While we were trying to avoid transmission with less transmissible variants, eleven Georgia children died of COVID-19. What happens when we put children into a school setting with a much more transmissible variant and no attempts to stop transmission?
References
https://covid-gagio.hub.arcgis.com/apps/georgia-medical-facility-patient-census/explore
https://dph.georgia.gov/covid-19-daily-status-report
https://epidemiologyschoolreport.s3.amazonaws.com/SchoolAgeSurveillance0712.html
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My Ph.D. is in Medical Microbiology and Immunology and I am Chair of the Division of Natural Sciences and Mathematics at the University of Saint Mary. I've worked at places like Creighton University, the Centers for Disease Control & Prevention and Mercer University School of Medicine. All thoughts are my professional opinion, do not represent the views or opinions of my employer and should not be considered medical advice.