[ExI] The Japanese mystery: why so few COVID cases?

[Stuart LaForge]

https://www.embopress.org/doi/10.15252/emmm.202012481?fbclid=IwAR3YClOFxx3Vy6hOD0VqLCynrTxRQxrUigVvLfMhkxRqHPxST9VdEhGWSlk&

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Despite early exposure, its dense and aging population, and little  
social distancing measures, Japan reports low infection and low death  
from COVID‐19. Here, we speculate on and discuss the possible reasons  
that may account for this anomaly.

There is a lot of interest brewing as to why Japan has such low  
numbers of confirmed infected cases of the COVID‐19 disease, caused by  
the SARS‐CoV‐2 virus (Fig 1), despite its high population density  
(over 6,100 persons/sqkm in Tokyo, 2.4 times higher than New York  
City) and large percentage of high‐risk individuals over 65 years of  
age (about 26%, compared with 15% in the USA). In Singapore and Hong  
Kong, rapid and strict quarantine rules and contact tracing have  
helped to “flatten the curve”. In South Korea, mass testing and  
quarantine measures appear to have reduced the rate of new cases.  
However, Japan has not engaged in expansive testing, contact tracing,  
or strict quarantine measures and yet is reporting a slow growth rate  
of infected persons and a death rate that is currently just 1/10th of  
world average. It is difficult to make direct comparison of infection  
rates, because the number of tests per capita varies dramatically  
between countries. However, this low death rate cannot be simply  
explained by lack of testing or reporting, as no surge in death from  
respiratory syndromes has been reported either.
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Is it due to differences in the prevalence of underlying conditions?  
This one has me stumped.

Stuart LaForge