TAMPA, Fla. -- Doctors say there is mounting evidence of a link between a certain blood type and the severity of the novel coronavirus.
A recent study included almost 2,000 patients with severe COVID-19 in Italy and Spain. An extensive genetic analysis was performed, looking at more than eight and half million gene variations.
One of the genes groups was linked to blood types. Overall, they found people with Type A blood increased their risk by 45%.
The University of South Florida’s Dr. Charles Lockwood says other risk factors like age, diabetes, high blood pressure, lung or heart disease are known risk factors.
As we continue to learn more about this virus, Type A blood would add one more.
“The effects are additive,” explained Dr. Lockwood, the dean of USF’s medical school. “So if you're a 70-year-old who smokes and has emphysema, and has an A-positive blood type, I don't know that I would want to stray far from my house.”
People with Type O blood had a protective effect with 35% lower risk. That doesn't mean people with Type O blood are safe and don't have to take precautions, though.
The study also revealed another cluster of genes that may increase risk. Those genes regulate immune response and are linked to the ace receptors in respiratory track that bind to the virus and allow it to enter the cell.
Both of these discoveries may lead to targeted treatments.
The study did not reveal why blood type may increase risk, but there are a few theories.
One has to do with clotting, a known complication of COVID-19. People with Type O blood have fewer proteins that promote clotting.
They also found genes that code for blood type are close to others that regulate the immune system so that might be playing a role.
The difference in risk may also be linked to antibodies in the blood. People with most blood types, except AB, form antibodies to differing blood types; that's why it's so important not to give someone the wrong blood type in a transfusion.
Type A forms antibodies to B, Type B forms antibodies to A, and Type O creates antibodies to both A and B.
Some believe anti-a antibodies in Type O blood alone may be protective. Even though people with Type B blood have them too, they don't have the same benefit.