While I have been limited this blog to diabetes, I feel the need to join the forces fighting panic. Too many cite and seem to extrapolate incorrectly from the Case Fatality Rate (CFR) thrown around by the WHO. Keep in mind, the ‘W” in World Health Organization includes all the nations with poorer healthcare systems compared to the USA. Using this CFR number causes unnecessary alarm, so I have linked to a diagram illustrating a way of viewing infection data in a manner more in keeping with medical professionals.
The CFR is derived from the number of deaths divided by the number infected. For one, it does not take into account the excess number of deaths that WOULD HAVE OCCURRED even if the virus had been absent. Therefore the CFR overestimates to varying degrees, the overall impact on the population, depending upon the subgroup suffering an increased number of deaths.
What is not generally appreciated, difficult to calculate, but most important to grasp is the Mortality Rate. At the very base, a segment of the population is simply immune to infection. In HIV, certain people have CCR5 mutations. For all we know, certain people have ACE2 mutations in their lungs, not allowing the coronavirus to attach to lung cells.
At the next tier, not everyone in the community exhibits behaviors which places or placed them at risk. Many are familiar with risky HIV behavior. In contradistinction, those who work in the engine room of the Diamond Princess might not dine or bunk with the other crew members. Everyone else is at risk of exposure to the virus. (Howard Hughes tried to be in this group during his last year of life.)
Still not figuring into the CFR formula are those who are exposed to the virus, but avoid infection because of excellent hygiene. Perhaps they keep a 4–6 feet distance from others. Maybe they don’t linger in small confined spaces. More proactively, maybe they regularly wash their hands with soap and water. They never touch their eyes or nose with their fingers.
The size of these lower, unaccounted for tiers dwarfs those stacked above them. Most importantly, they differ significantly across different societies and countries. For those of you who have lived in China, you know that soap in public bathrooms is near non-existent, whereas smoking and spitting in public is ubiquitous. These customs make the same airborne disease, such as tuberculosis rampant. In developed countries, by contrast, TB is confined to very small, known subgroups.
For those of you citing coronavirus’ 10X lethality compared to influenza, please add these lower base tiers to your mental calculations of risk. Many more are exposed or at risk but do not get counted in CFR. Mortality Rate matters more than CFR to a population. The Diamond Princess debacle/experiment gave us excellent data in this regard (Base 3700, Test positive 696, Critically ill 32, Deaths 6; implied morality rate of 0.16%) China and Chinese do not have the same living conditions, personal habits, or hygiene. Not only did these factors give rise to coronavirus, but accelerated its explosive spread. We should take comfort when applying the cool, considered logic to epidemiology.
