COVID-19 global deaths

Introduction

ascertaining the extent of deaths due to a pandemic is not easy for many reasons such as:
- many countries have pre-existing poor death registration systems
  - these issues are exacerbated when death rates increase and systems are over-whelmed
- doctors may not include the disease on the death certificate because:
  - patient had not been tested for it prior to death
  - patient had co-morbidities which could explain the death hence many in Aged Care with advanced dementia may just have the dementia as the cause of death to expedite the process.
  - deceased was only swabbed post-mortem and results are not available before the death certificate was written
  - potential political interference in the medical autonomy to decide or to test
  - the pathogen could cause or exacerbate another condition which then was the direct cause of death without the infection being clearly evident - many elderly people do not develop fevers and may just become delirious with an infection
- indirect deaths resulting from the pandemic such as:
  - effects of lockdowns on care, mental health, etc
  - hospital systems being overwhelmed resulting in poorer access and higher mortality for non-pathogen diseases or trauma
  - reluctance for people to present to healthcare during a pandemic resulting in delayed diagnosis and treatment such as for cancers
in the best of times, a state's mortality records are significantly retrospective in nature to achieve reasonable accuracy and thus not conducive to accurate estimates when requested in real time

Estimating real mortality rates

the "Excess Deaths" method

this compares actual recorded deaths from all causes with that which would normally be expected taking into account the season - there is often a small hump in Winter due to seasonal influenza, etc.
this gives a reasonably reliable estimate but unfortunately cannot distinguish deaths directly caused by the pathogen versus indirect causes of death without the infection being present
furthermore, it can only be calculated on the basis of accurate, high-frequency data on mortality from previous years and few countries can provide this
this can be measured as a P-score or Percentage difference compared with similar period in past years
see https://ourworldindata.org/excess-mortality-covid for more details and charts

Covid-19 and overall mortality in various countries to Aug 2020 (source: Nature Sept 2020: How many people has the coronavirus killed?):