Infectious Diseases

A-Positive Blood Type Linked to 45% Increased Risk of COVID-19 Respiratory Failure

Posted on 5 June 2020

At the time of writing, COVID-19 has claimed over 390 thousand lives around the world, with a key driver of mortality being respiratory failure. While conditions such as cardiac disease, pulmonary diseases and diabetes undoubtedly increase the risk of severe illness, we still don’t fully understand why some people develop respiratory failure while others do not.

Now, a genome-wide association study published in the preprint journal medRxiv suggests that blood type might play a role in determining risk of COVID-19 respiratory failure. The study recruited 1610 patients with COVID-19 respiratory failure and 2205 controls from Spain and Italy, with the aim of identifying genetic risk factors.

Understanding Blood Types
Stories, N., Types, U., & Types, U. (2020). Stories. Retrieved 5 June 2020, from

A total of 8,582,968 single-nucleotide polymorphisms (SNPs) were analyzed, and a meta-analysis of the Italian and Spanish cohorts was conducted.

A lead SNP was […] identified on chromosome 9 at the ABO blood group locus, and further analysis showed that A-positive participants were at a 45% increased for respiratory failure, while individuals with blood group O were at a 35% decreased risk for respiratory failure.

The authors say that early clinical reports have suggested the ABO blood group system is involved in determining susceptibility to COVID-19 and has also been implicated in susceptibility to SARS-CoV-1.

Sally Robertson, B. (2020). Blood group type may affect susceptibility to COVID-19 respiratory failure. Retrieved 5 June 2020, from

The authors note that variations at the ABO blood group locus have previously been linked to increased levels of the inflammatory mediator IL-6, as well as increased markers of blood coagulation, both of which are associated with COVID-19 mortality.

However, this was not all the authors found: they also identified a gene associated with severe COVID-19 called SLC6A20. This gene codes for a protein called Sodium/Imino-acid Transporter 1 (SIT1), a transporter that is expressed by cells in the alveoli. This transporter interacts with angiotensin-converting enzyme II, the protein used by SARS-CoV-2 to gain access to human cells, and the authors suggest that SIT1 should be investigated for its potential role in viral entry.


The ABO blood group locus and a chromosome 3 gene cluster associate with SARS-CoV-2 respiratory failure in an Italian-Spanish genome-wide association analysis:

Blood group type may affect susceptibility to COVID-19 respiratory failure:

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