How does the coronavirus choose its victims? This is a question that has plagued the minds of doctors, scientists, and families ever since the battle with COVID-19 began. Scientists first believed that age was the most influential factor when it came to virus susceptibility. However, as the pandemic progressed, doctors found themselves with young, healthy patients in need of urgent treatment and older, weaker patients who dodged the bullet. So, scientists began to look for answers again. Recently, a genetic study of coronavirus patients from Italy and Spain, revealed that individuals with type A blood are at higher risk of going into respiratory failure than individuals with type O blood. This new discovery supports the theory that people with type A blood are more vulnerable to the virus while type O blood provides some form of protection. With these findings, a new question emerges: what’s the correlation between coronavirus and blood type?
In the study, scientists sequenced the genomes of more than 1610 COVID-19 patients who had been hospitalised due to respiratory failure and analysed the differences in their genetic sequences in comparison to 2205 healthy people. They discovered two areas of DNA in which the genetic differences were connected to the severity of disease one of which was the region that holds the gene coding for an individual’s blood type. Another study by genomics and biotechnology company 23andMe came to the same conclusion. They released preliminary results from a study of 750,000 people which shows that people with type O blood, have a greater defense against COVID-19 in comparison to other blood types. Their data suggest that individuals with type O blood are 9-18% less likely to contract the virus. Data from patients at New York-Presbyterian Hospital revealed that people with A-type blood are 33% more likely to contract the virus. Of the 1559 people tested, 682 tested positive. Research done by scientists in China examined the connection between the ABO blood group and coronavirus vulnerability. They compared the blood type of 2173 COVID-19 patients in Wuhan and Shenzhen to healthy people and also discovered that blood type A is correlated to a higher risk of disease while blood type O is correlated to a lower risk of illness.
Blood type is determined based on the presence of A and B antigens. If the A antigen is present, the person has type A blood. If the B antigen is present a person has type B blood. If neither are present, the individual has type O blood. Whether someone has a positive or negative blood type, is determined by the presence of the Rh factor protein. Glycobiologist Jacques Le Pendu, says that “SARS-CoV-2 can replicate in cells that express blood type antigens”. This means that when someone with the virus coughs or sneezes, they could be unleashing viral particles covered in their blood type antigen. So, if an infected person with A blood passes the infection to someone with type O blood, the person with O blood has antibodies to fight the infection. However, if an infected person with A blood infects someone who also has A blood, that individual does not carry the antibodies that fight the infection.
Research from the SARS epidemic also provides evidence to support these ideas. A report containing the data from a breakout in Hong Kong shows that of the 45 people exposed, 19 carried type O blood and 26 carried the other blood types. Of the people with O blood, only 8 fell ill. Of the people with other blood types, 23 contracted the disease. Le Pendu discovered that antibodies against the type A antigen prevented the SARS-CoV-1 protein from infecting cells but only if the virus protein was replicated in cells that could express the antigen.
Although there is evidence to support the idea that people with type O blood are at lower risk for infection, some scientists argue that the conclusion doesn’t support infection rates in the United States. Type O blood is more common in African Americans yet they face high disease rates. Researchers argue that this data proves that blood type plays a limited role in the transmission of disease. University of Michigan’s director of immunohematology, Laura Cooling, says that “It’s what your blood type is, relative to the other person who exposed you, relative to all the other genetic and acquired health conditions you have”. Still, it is clear that blood type plays some type of role in the transmission of disease.
The presence of antigens is not the only way blood type influences the risk of infection. It can also influence the likelihood of blood clotting which has proven to be a factor in the risk of infection. People who carry type O blood, also carry lower levels of proteins that contribute to blood clotting. Fumiichiro Yamamoto, an immunohematologist at the Josep Carreras Leukaemia Research Institute says that “this also strengthens the argument that group O individuals are least likely to be severely damaged by this disease”.
Scientists are still in the early stages of research into this correlation, and are conducting further investigation to continue to test out the conjecture that there is a relationship between Blood type and Coronavirus.
Alla Katsnelson, special to C&EN. “Genetic Study Suggests That People's Blood Type May Affect Their COVID-19 Risk.” Chemical & Engineering News, American Chemical Society, 15 June 2020, cen.acs.org/biological-chemistry/infectious-disease/Genetic-study-suggests-peoples-blood/98/i23
“Blood Types.” Explained - A, B, AB and O | Red Cross Blood Services, www.redcrossblood.org/donate-blood/blood-types.html.
Staff, Live Science. “Why COVID-19 Kills Some People and Spares Others. Here's What Scientists Are Finding.” LiveScience, Purch, 19 June 2020, www.livescience.com/why-covid-19-coronavirus-deadly-for-some-people.html.
Zhao, Jiao, et al. “Relationship between the ABO Blood Group and the COVID-19 Susceptibility.” MedRxiv, Cold Spring Harbor Laboratory Press, 1 Jan. 2020, www.medrxiv.org/content/10.1101/2020.03.11.20031096v2.