COVID-19 true death toll: Calculating excess mortality

The number of people infected by the novel coronavirus infection caused by the SARS-CoV-2 virus continues to rise around the world, with the Johns Hopkins University and Medicine's Coronavirus Resource Center and Worldometer reporting more than 15.9 million cases globally as of 25 July 2020.

And as the death toll due to COVID-19 went past the 640,000-mark recently, there have been growing concerns over whether these numbers are in fact accurate, or whether there is more to looking at the total number of people who have perished from this viral infection.

Yet, the study of mortality figures isn't anything new; in fact, it dates back centuries to the plague outbreak of the 17th century in Europe, which was dubbed the Black Death. As many as 70,000 people were reported to have died due to the disease in the city of London alone, and even this data collection was only possible as city officials introduced bills into law that would report every death that occurred in their local region.

Read more: Zoonotic diseases

Today, tracking mortality data has become an important tool in the field of public health and epidemiology to assess the burden of a particular disease or factor in a certain population.

Databases maintained by epidemiologists around the world suggest that the true extent of the damage (read deaths) caused by COVID-19 could be far higher than the numbers being presented by government authorities all over the world. This phenomenon, however, is not new and is known in the world of epidemiology as excess mortality.

What is excess mortality
Excess deaths
Limitations in reporting accurate figures

What is excess mortality

Excess mortality refers to the deaths that have occurred outside of the traditional markers of the causes of deaths from an infectious disease. Because the causes of deaths due to COVID-19 are plenty and there are several factors outside of immediate infection that have led to fatalities, excess mortality helps us understand the true impact of a global pandemic. These figures and data have been used in the past not only to report on true mortality figures from infectious diseases, but also to report on several other issues, such as mortalities due to natural disasters as well.

Official government data, at least in the case of COVID-19, are based on the actual number of tests that have been carried out at district, state and national levels, and the corresponding figures of positive and negative cases, as well as deaths caused by the disease.

However, there is much more to it than that when it comes to actual figures when one factors in irregularities in the tracking of data, misdiagnosis or even those who have not been tested or treated, as well as deaths that have occurred without a direct link to the infection.

According to the World Health Organization, excess mortality is defined as something "above what would be expected based on the non-crisis mortality rate in the population of interest. Excess mortality is thus mortality that is attributable to the crisis conditions. It can be expressed as a rate or as a total number of excess deaths".

According to ourworldindata, a database dedicated to global testing statistics, the limitations countries face regarding testing or the inability to attribute the true cause of deaths indicate that the true death toll could be far higher than those that are given out. There are three key factors to keep in mind regarding confirmed death figures and statistics:

The true death toll from COVID-19 could be far higher than the number of deaths due to limited testing (or not even standardised methods of testing), as well as not being able to attribute the right cause of death.
The methodologies adopted by different countries in recording the number of deaths may be different. This can be understood by some countries only reporting deaths that occurred in hospitals, while some include deaths that have taken place at home or elsewhere.
There is a delay in reporting daily death counts, which leads to inaccurate daily death figures.

This may also be true in the case of India, which so far has reported a total of 31,358 deaths according to Johns Hopkins University data. However, the limitations in the number of tests being carried out on a daily basis, in different states, districts and cities of the country mean that every individual state itself may have different figures than each other.

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Excess deaths

Certain countries have begun analysing and reporting more concrete information on deaths at a faster rate, on account of the need for accurate figures. Certain countries such as France and Belgium adjusted their official death figures by adding deaths due to COVID-19 that occurred outside of hospitals (such as retirement homes) in their daily death reports.

While the number of infections and deaths surged in Wuhan, China, in the early months of the outbreak of COVID-19, as countries like South Korea, Iran and Italy began to report significantly higher numbers, China's number of cases stagnated. However, authorities in Wuhan revised the COVID-19 death toll in April and added another 1,290 deaths to the official figures, taking the total number of deaths to 3,869.

A study looking into Italy's death figures indicated that the true death rate in the country's worst affected areas could be 1.5 times more than the official figures. It is worth noting that Italy was one of the countries that were worst-hit by the coronavirus infection—Italy was overwhelmed by the rate of infections and deaths early in 2020.

Another similar database known as EuroMOMO that collects reports on deaths due to various causes all over Europe suggests that the total death figures due to COVID-19 are much higher than mortalities from the seasonal flu since the year 2016. They go on to report that the number of excess deaths on the continent since the month of March 2020 is around 170,000!

According to a UNDP Latin America report looking into the excess mortality rates in countries such as Brazil, Chile, Mexico and Peru, "the number of confirmed deaths vastly underestimates the actual death toll from the pandemic". Death figures are significantly underreported in various areas of Brazil. For instance, as the city of Rio de Janeiro reports about 32% of deaths not being taken into official death figures, the city of Manaus has a staggering 80% of deaths that have not been taken into account.

Limitations in reporting accurate figures

The UNDP adds that the problem of underreporting is not solely due to a lack of testing capacity by certain countries, but there are many more factors that go into it. Besides the above-mentioned factors of deaths outside of hospitals or those who died without being tested for COVID-19 not being included in official figures, there are inconsistencies in the method used for testing as well, as certain rapid tests aren't of the same quality as other testing methods, and may not indicate accurate results.

Institutional lockdowns imposed in several parts of the world have also led to a drop in mortalities due to other factors such as road accidents or other health issues, but at the same time, there may have been a spike in deaths due to a lack of treatment for other illnesses and diseases which were not being treated with the same urgency due to the threat of contracting COVID-19.

Some countries genuinely lack the infrastructure or the resources to carry out large-scale testing to be able to report actual figures, which leads to irregularities in the reporting of true death figures from the disease. In fact, even excess deaths aren't the most accurate in terms of calculating the true death toll due to COVID-19, but an indicator that helps in understanding the extent of the spread of the disease. It also goes a bit further than official government death figures would have us know, so that better, more improved methodologies can be incorporated in a bid to take corrective or precautionary measures.