What do you know: putting Covid-19 into context

August 30, 2021

Photo Credit: fernando zhiminaicela / Pixabay

By Andrew Hillman

This story was created as part of my practice-based research project for my Master’s in Data Journalism. The project explored the use of prediction-oriented data visualisation and mobile-first design of interactive visualisations. Note that the data has not been updated since the publication date.

Covid-19 has dominated our way of life, daily conversations and the news for the past 18 months, but does that mean we all have a good understanding of the virus’s impact? Drag the circles on the graphs below to set your predictions and then see how they compare to the actual figures.

In May, Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, described the Covid-19 pandemic as “unquestionably the worst pandemic of an infectious disease that the planet has experienced in 100 years.”

Observing the number of confirmed deaths due to Covid-19, the veracity of Fauci’s statement is clear. Despite mass testing programmes, unprecedented restrictions on movement and social gathering, and vaccines developed in record time, fatalities due to Covid-19 comfortably exceed those of recent pandemics.

It is also clear that to this point, Covid-19 has been less destructive than a strain of avian influenza, dubbed the Spanish flu, which swept across the world just over a century ago. Spanish flu is believed to have infected one in three people globally, with an estimated death count between 17 and 100 million people – an extraordinary 1-6% of the population at the time.

In England and Wales, life expectancy fell by 13 years during the Spanish flu pandemic. In comparison, from 2019 to 2020, life expectancy in England declined by just a single year as the country was hit by Covid-19.

Estimating the number of people who died due to the Spanish flu has proven difficult because of an absence of testing at the time and incomplete deaths records. A century later, these factors continue to make understanding the impact of infectious diseases a challenge.

In April, as the new Delta variant rapidly spread through India, multiple states reported Covid-protocol cremations – conducted when the deceased was believed to have died with Covid-19 – which were more than ten times higher than officially reported deaths due to the virus.

Official figures put India’s Covid-19 death toll at 438,000, but analysis focusing on excess deaths – the number of deaths above what would be expected based on historical data – suggests the true figure is far higher. In July, research by the Centre for Global Development, a Washington think tank, concluded that the actual number is between 3.4 and 4.7 million. Another study by the Center For Voting Opinions and Trends in Election Research in India and the School of Public Health at Toronto University estimated 3.1 to 3.4 million deaths.

To account for underreporting at a global level, The Economist developed a predictive model for estimating total excess deaths. First they calculated excess deaths for countries where accurate mortality data was available. For remaining nations, The Economist looked at other measures, including official case and death levels, test positivity rates and mobility data. They then combined this data with mortality data for other countries with similar characteristics, effectively asking: what were excess death levels in neighbouring countries, or in countries with similar demographic profiles?

Based on their model, The Economist predicted that by May 2021, there had been 10.2 million excess deaths globally since the beginning of the pandemic – triple the number of confirmed deaths due to Covid-19. This mortality rate – an average of 24,500 excess deaths per day – can be compared to the two most common causes of death in a typical year: it is similar to the number of deaths caused by cancer, and approximately half the average daily deaths due to cardiovascular diseases.

Misinformation surrounding Covid-19 has been common, particularly on social media, and one pervasive claim was that the virus was no worse than the flu. But globally, Covid-19 is significantly more deadly than seasonal flu. Despite restrictions to limit the spread of the virus, the number of excess deaths during the pandemic is almost 20 times higher than the number of deaths which we would expect due to seasonal flu over the same period.

Covid-19 has led to more deaths than seasonal flu in part because the virus has a higher case-mortality rate – the probability that a Covid-19 infection will result in death. In the UK population, the case-fatality rate prior to the vaccination rollout was estimated to be between 0.5% and 1%. Seasonal flu’s case-fatality rate is believed to be around 0.1% - five to ten times lower.

Another factor is that Covid-19 is more transmissible, meaning more people have been infected by the virus than by flu since the pandemic began. With the original strain of Covid-19, each infected individual would, on average, infect three other people. Strict lockdowns brought this reproduction rate below one, but over time the virus has mutated to become more transmissible – with the Delta variant an infection, in the absence of restrictions, will lead to a further seven cases. In comparison, without restrictions seasonal flu has a reproduction rate of approximately 1.3.

Focusing on excess deaths means incorporating changes in mortality that were not directly caused by Covid-19, but were instead driven by societal responses to the virus. For instance, in the UK travel restrictions during the first six months of the pandemic led to 20% fewer deaths in road accidents. This trend was not consistent across countries however: in the US and Japan, fatalities due to road accidents increased during lockdowns as drivers travelled faster on quieter roads.

In many countries a combination of social distancing and the diversion of medical resources to treat Covid-19 patients led to delays in treatment for other conditions. In the UK, the number of referred patients required to wait in excess of a year to receive treatment from the National Health Service peaked in March at 436,000, compared to just 3,100 patients twelve months earlier.

Many of these delays to diagnosis or treatment are for serious illnesses – for example, 40,000 fewer people began receiving treatment for cancer in 2020 compared to the previous year, according to Cancer Research UK. These delays have not yet led to an observable increase in preventable deaths, but fears continue that even if Covid-19 deaths remain low in future months, excess deaths due to other causes may rise.

Another consequence of lockdowns and social restrictions has been less transmission of seasonal flu. This may partly explain why some countries which have kept deaths from Covid-19 very low – such as Australia, New Zealand and South Korea – have actually experienced negative excess deaths. In other words, these countries have seen fewer total deaths during the past 18 months than would have been expected had the pandemic never occurred.

At the opposite end of the scale, Peru has the highest excess death rate of all nations with accurate mortality records, despite the Peruvian government imposing strict lockdowns. Russia also has a high excess death rate, in sharp contrast to its official count of confirmed Covid-19 deaths, which is lower than the UK’s.

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