Objective: To review the literature on the association between ABO blood groups and diseases, including Sars-CoV-2 (COVID-19).

Methods: Conducted a literature search in google and Pubmed on blood groups and disease associations. Twenty-five reports were analyzed.

Results: Significant associations have been reported between specific blood groups and diseases including malaria, cholera, cancer, cognitive impairment, heart disease, hypertension, clotting disorders, longevity, and even intelligence quotient. Recently a number of studies have reported an association between individuals with blood group A and increased risk of infection and severity of disease with COVID-19 infection whereas Group O individuals had significantly less risk.

Conclusion: ABO blood groups are associated with the susceptibility and severity of certain diseases. However, they do not necessarily cause diseases as there are likely a number of confounding variables or linked genetic loci. Nevertheless, ABO blood groups may be a contributing factor in specific diseases including COVID-19 infection.