According to today’s data from John Hopkins University https://coronavirus.jhu.edu/map.html , the United Kingdom has a Case Fatality Rate (CFR) of 15.5%, this means that for every 6 & 1/2 people diagnosed with COVID-19 in the UK, one will die. However, the CFR for Australia is 1.33%. Both of these countries share a similar heritage, wealth and good medical systems. So why the huge difference?
University of Queensland virologist Ian Mackay said that testing is likely to be the key: ‘My crude presumption has been that in jurisdictions where rates of death are above 1%, there has been too little testing to capture the denominator,’
The Oxford University Centre for Evidence Based Medicine (CEBM) postulates the following reasons that the CFR varies so greatly country by country:
- The number of cases detected by testing will vary considerably by country
- Selection bias can mean those with severe disease are preferentially tested
- There may be delays between symptoms onset and deaths, which can lead to underestimation of the CFR
- There may be factors that account for increased death rates such as coinfection with another disease, more inadequate healthcare and patient demographics
- There may be increased rates of smoking in some countries or comorbidities (such as cardiovascular disease) amongst the fatalities
- Countries with populations that are older get worse hit by COVID-19 (eg: Italy with the 2nd oldest population in the world)
- Differences in how deaths are attributed to coronavirus – dying with the disease (association) is not the same as dying from the disease (causation)
Another point to note is that COVID-19 may not be as fatal as the “Case Fatality Rate” implies. CFR rates are subject to selection bias as more severe cases are tested – generally those in the hospital settings or those with more severe symptoms. The number of currently infected asymptomatic people is uncertain: estimates put it at least a half are asymptomatic; the proportion not coming forward for testing is also highly doubtful (i.e. you are symptomatic, but you do not present for testing). Therefore we can assume the IFR (infection fatality rate) is significantly lower than the CFR.
Read full article on: cebm.net
Dr Lachlan Soper