A hot topic. Specifically, because Case Fatality Rates (CFR) are decreasing, while cases are increasing. Which seems counter intuitive.
I’ve seen several hypotheses floating around explaining this phenomenon:
1. Lag time. Scientists have estimated that CFR lags 14-30 days due to disease manifestation and spread to vulnerable populations. So, for example, the CFR on July 7 isn’t reflective of the cases on July 7 but INSTEAD is reflective of the spread on June 5. Exponential growth started in Texas on June 15ish and 30 days have yet to pass. We may see this start to increase here soon. This delay has a big impact on CFR (see how different the 14-day lag compared to the 30-day lag is in the Figures).
2. Younger populations. Younger people are contracting and spreading COVID19, which mean younger people are going to the hospital more, but once at the hospital they are dying at a slower rate. Keep in mind that “not dying” is not the same thing as “fully recovering”. The younger population also might contribute to #1 (lag time). If there is a lot of spread among younger populations, then the time for COVID19 to get to the more vulnerable will take longer.
3. Treatment. Compared to the beginning of the pandemic, doctors have figured out better ways to treat COVID19. For example, dexamethasone cuts risk of death on a ventilator by 1/3 and those on oxygen by 1/5. Also, plasma transfusions have helped patients recover.
4. Mutation. Since the pandemic started there have been 33 COVID19 mutations. Scientists recently published that the latest strain MAY be more contagious. Could it also be less deadly? There still needs to be a LOT more studies on this, but an important question.
5. Hospital capacity. Texas hospitals have held their own. BUT if cases don’t stop rising, hospitals in some areas will run out of surge units, staff, supplies, etc. If this happens, CFR will increase again regardless of #1-4.
CFR decreasing is fantastic. It’s likely to a combination of the 5 above. However, I’m skeptical that it will stay this way. Unfortunately, only time will tell the bigger picture.
It’s important to note that even if CFR is decreasing, 2% is incredibly devastating. In Texas, COVID19 still is the 7th leading cause of death and 3rd leading cause of death in the US. Compared to other leading causes of death (heart disease, cancer), it’s only been around for FOUR MONTHS and is contagious.
Love, your local epidemiologist
Data source: DSHS. Graphs by yours truly.
Mutation study: https://www.biorxiv.org/…/10.1…/2020.06.12.148726v1.full.pdf
Dexamethasone study: https://www.medrxiv.org/conte…/10.1101/2020.06.22.20137273v1