Paradoxical Case Fatality Rate dichotomy of Covid-19 among rich and poor nations points to the “hygiene hypothesis”

  1. Bithika Chatterjee
  2. Rajeeva Laxman Karandikar
  3. Shekhar C. Mande

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Abstract

In the first six months of its deadly spread across the world, the Covid-19 incidence has exhibited interesting dichotomy between the rich and the poor countries. Surprisingly, the incidence and the Case Fatality Rate has been much higher in the richer countries compared with the poorer countries. However, the reasons behind this dichotomy have not been explained based on data or evidence, although some of the factors for the susceptibility of populations to SARS-CoV-2 infections have been proposed. We have taken into consideration all publicly available data and mined for the possible explanations in order to understand the reasons for this phenomenon. The data included many parameters including demography of nations, prevalence of communicable and non-communicable diseases, sanitation parameters etc. Results of our analyses suggest that demography, improved sanitation and hygiene, and higher incidence of autoimmune disorders as the most plausible factors to explain higher death rates in the richer countries Thus, the much debated “hygiene hypothesis” appears to lend credence to the Case Fatality Rate dichotomy between the rich and the poor countries.

Significance

The current COVID-19 epidemic has emerged as one of the deadliest of all infectious diseases in recent times and has affected all nations, especially the developed ones. In such times it is imperative to understand the most significant factor contributing towards higher mortality. Our analysis shows a higher association of demography, sanitation & autoimmunity to COVID-19 mortality as compared to the developmental parameters such as the GDP and the HDI globally. The dependence of sanitation parameters as well as autoimmunity upon the mortality gives direct evidences in support of the lower deaths in nations whose population do not confer to higher standards of hygiene practices and have lower prevalence of autoimmune diseases. This study calls attention to immune training and strengthening through various therapeutic interventions across populations.

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  2. Version published to 10.1101/2020.07.31.20165696v2 on medRxiv
  3. Version published to 10.1101/2020.07.31.20165696v1 on medRxiv