The questionable value of the CDC's Community Levels

Last update: Friday 9/23/22 

Editor's apology: OK, the image for this blog note is attention-grabbing click bait. Our planet is not being attacked by a gigantic, intergalactic, spiked-headed coronavirus. However, out-sized bad guidance from the CDC should be just as improbable. Nevertheless, it keeps happening. So here's a brief recap of a recent "attack" and a warning.

Community Levels

The CDC and other public health agencies have recommended varying levels of mitigations from the beginning of the pandemic in efforts to reduce the maximum levels of surges in infections and thereby reduce the maximum levels of the inevitable subsequent surges in severe illness that requires hospitalization that usually followed a few weeks later. If the mitigations were successful, the subsequent surges in hospitalizations would not rise so high as to overwhelm the maximum holding capacities of our hospitals and other health care facilities. 

• In principle, it should have been possible to develop algorithms that used data that measured the steepness of the infection curves at the beginning of an infection surge in a community to predict the maximum height of the subsequent surge in hospitalizations in that community.
  
  
• Once reliable prediction algorithms were developed, if the beginning of a surge were steep enough, their predictions of a pending overload of a community's hospitals a few weeks later could alert local public health officials and members of the community to the need to immediately increase their mitigations to higher, more restrictive levels, e.g., resume wearing masks, keeping social distancing, etc. 
  
  
• More restrictive mitigations would reduce the actual increases in infections from week to week that subsequently occurred, and thereby reduce the maximum hospitalizations a few weeks later below the maximum holding capacities of the community's hospitals and other health care facilities
  
  
• The CDC announced its implementation of these notions on 2/25/22. Its "COVID-19 Community Levels" page classified all U.S. counties into four levels: Low, Moderate, Substantial, and High, depending on the steepness of thire infection curves. The weakest mitigations were recommended for Low counties; the strongest mitigations were recommended for High counties.

The CDC developed the notion of Community Levels before Omicron emerged as the dominant variant. Unfortunately, 2/25/22 was well into the Age of Omicron. Omicron (all variants) differed from Delta and previous variants in significant ways

• Omicron is milder, i.e., the death rate per 100,000 people infected by Omicron is lower than the death rate per 100,000 infected by previous variants
  
  
• Indeed, most people infected by Omicron are asymptomatic or have such mild symptoms that they don't know they have been infected. (See "Awareness of SARS-CoV-2 Omicron Variant Infection Among Adults With Recent COVID-19 Seropositivity", Sandy Y. Joung, MHDS1; Joseph E. Ebinger, MD, MS1; Nancy Sun, MPS1; et al, JAMA, 8/17/22)
  
  
• However, Omicron is far more transmissible, e.g., more people are infected during surges each week by Omicron than were infected each week during surges of new infections  by previous variants
  
  
• Moreover, more people have become reinfected by Omicron than by previous variants (See "You Are Going to Get COVID Again … And Again … And Again", Katherine J. Wu, The Atlantic, 5/27/22)

Additional complications arose from changes in testing under Omicron

• Many (most?) COVID tests are now self-tests that are not reported to anyone
• Self-tests yield more false negatives than PCR tests administered by professionals

Taken together, these considerations strongly imply that the CDC's estimates of the number of new infections in U.S. counties each week are probably way, way, way below the actual values. In other words, the level of the virus spreading through a community will probably be much higher than the CDC's estimate. 

Readers should never forget the fundamental reality of COVID in all of its variants: COVID doesn't kill everyone. Over 90 percent of the victims killed by COVID have been of age 50 or older. And the vast majority of its younger victims, the other 10 percent, have had specific health conditions that made them especially vulnerable to COVID, e.g., immunocompromised, diabetic. Therefore Community Level false negatives reported by the CDC that suggest that mitigations can be relaxed may pose mortal threats to those made vulnerable by age and/or health conditions. 

Warning
Vulnerable potential victims of COVID and their families, friends, and professional associates who see them face-to-face frequently should should ignore the CDC's Community Levels. Instead, they should maintain risk-averse mitigations until the pandemic is really over.

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Links to related notes on this blog:  

• 4 COVID FAQs, Last update:9/15/22