Case fatality rates for COVID-19 and health indicators

By Dr. Ananya Mandal, MDSep 29 2020

Researchers from Turkey and Switzerland collaborated to study the nation-specific case fatality rates for COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The pandemic has affected around 33.5 million people worldwide and killed over 1 million making it one of the largest global health crises in recent memory.  This new study titled, “National case fatality rates of the COVID-19 pandemic” was published in the latest issue of the journal Clinical Microbiology and Infection.

Study: National case fatality rates of the COVID-19 pandemic. Image Credit: Corona Borealis Studio / Shutterstock

What was the study about?

The SARS-CoV-2 leads to a varied range of illnesses ranging from mild respiratory illness to severe acute respiratory distress, leading to death. The authors of the study wrote that case fatality rates (CFR) of Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) were 9.5% and 34.4%, respectively. The CFR for SARS CoV-2, however, is found to be much lower. The infectivity of this virus, however, is very high with an R0 of 3. Due to the high risk of transmission, the chances of spread of this virus is more significant and as a result, it has resulted in more deaths,

Data sources

Different studies published to date on CFR of COVID-19 have a vast difference in numbers, and this significantly varies between nations wrote the researchers. They suggest the mathematical models could help determine the mortality based on health indicators and covariates. This would help develop tools to combat the spread of this pandemic effectively.

The purpose of this study

The main objective of this study was to identify the health indicators and covariates that could influence the CFR due to COVID-19 in different countries of the Organization for Economic Co-operation and Development (OECD). These indicators could help predict if the country was prepared to combat the pandemic. They hope that their analysis would help these countries increase and improve their response to the ongoing pandemic.

What was done?

For this study, the researchers identified health indicators for each country where COVID-19 cases were seen. A total of 18 variables were extracted from international administrative data sources of the 34 member countries of OECD. They also identified 16 variables in multivariable analysis. Then the team developed a dynamic web-based model to analyze the associations for the CFRs of COVID-19 in the countries. They followed the Guideline for Accurate and Transparent Health Estimates Reporting (GATHER) system for their analysis.

The variables for major non-communicable and communicable diseases and other factors included in the study were;

• Diabetes prevalence in ages 20-79
• Cancers prevalence in ages over 15
• All cancers incidence in ages 15+ per 1,000 people
• Obesity in adults
• Hypertension in adults
• Tuberculosis incidence per 1,000 people
• HIV/AIDS prevalence in ages 15-49 years
• The median age of the population
• Percentage of population over age 65 years
• Percentage of the male population
• Tobacco smoking in ages over 15 years

Variables related to the healthcare system were;

• Hospital beds per 1,000 people (hospital bed density)
• Number of nurses and midwives per 1,000 people (nurse and midwives density)
• Number of doctors per 1,000 people (doctor density)
• Number of tests per 1,000 people (test rate)

Variables related to the country:

• Gross domestic product (US dollars per capita) (GDP)
• Health spending (US dollars per capita)
• Rural population percentage (rural population ratio)

Case fatality was calculated, and analysis of duration since first death (days) (duration since first death) was included in the model.

What was found?

This was a multivariate analysis, and some of the variables were found to be significantly associated with the increased CFRs. These were;

• Obesity in ages >18 years
• Tuberculosis incidence
• Duration (days) since first death due to COVID-19. The team writes, “Many of the 34 OECD-member countries have not reached the peak level of the pandemic yet, therefore as the time progresses since the first death, the CFR still increases.”
• The median age of the population

Certain factors were significantly inversely related to CFR of COVID-19. These were;

• COVID-19 test rate
• Hospital bed density
• Rural population ratio

Conclusions and implications

The authors concluded that the pandemic was worst in population-dense cities worldwide, and it was here that death rates were higher. They urged governments to increase test rates and enable more effective diagnostic tests. In countries with older individuals and those with obesity were also at a greater risk of worse outcomes of COVID-19. Those caring for older persons and obese individuals should be warned about a potentially increased risk, wrote the researchers.