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Blood types and coronavirus: are certain types more susceptible to Covid-19?

Usually your blood type makes little difference in your daily life unless you need a blood transfusion.

However, people with type A may be at higher risk of getting Covid-19 and develop severe symptoms, as recent research has shown, while people with type O blood have a lower risk. These study results follow Evidence from previous research shows that certain blood types are more susceptible to other diseases, such as cancer.

But why we have blood groups and what they do is still largely unknown, and very little is known about their connections to viruses and diseases. Identifying the role of blood types may help scientists better understand the risk of disease for people in different blood types.

“I find the evolutionary story fascinating, although I don̵

7;t think we have the answer to why we have different blood types,” said Laure Segurel, a human evolutionary geneticist and researcher at the National Museum of Natural History in France.

Why are they important?

The blood groups were determined in 1901 by the Austrian immunologist and pathologist Dr. Karl Landsteiner discovered, who later received a Nobel Prize for his work. Your blood type is like other genetic traits inherited from your parents.
Before blood groups were discovered, transfusion, a now life-saving procedure, was a high-risk, high-risk process. The pioneer doctor Dr. James Blundell, who worked in London in the early 19th century, gave blood transfusions to 10 of his patients – only half survived.
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What he didn’t know is that people should only get blood from certain other people.

Here’s why: Your ABO blood type is identified by antibodies that are part of the body’s natural defense system and antigens, a combination of sugar and proteins that cover the surface of red blood cells. Antibodies recognize all foreign antigens and instruct your immune system to destroy them. Therefore, giving blood from the wrong group to someone can be life threatening.

For example, I have blood type A +. If a doctor accidentally injected me with type B, my antibodies would reject and break down the foreign blood. As a result, my blood would clot, interfere with my circulation and cause bleeding and difficulty breathing – and I might die. But if I got Type A or Type O blood, I would be fine.

Your blood type is also determined by Rh status – an inherited protein found on the surface of red blood cells. If you have it, you are positive. If you don’t, you are negative.

Most people are Rh positive, and these people can get blood from negative or positive blood type matches. However, people with Rh-negative blood should normally only receive Rh-negative red blood cells (as your own antibodies may react with the incompatible donor blood cells).

This gives us eight possible primary blood types, although there are some rarer ones.

Evolutionary puzzle

It’s not just people who Blood types have – at least 17 different types of primates, including chimpanzees and gorillas. Evolutionary biologists have found that blood types are deeply old and 20 million years old because of a distant ancestor that we shared with primates.

“Many primate species … also have the differences of being A, B, AB,” said Segurel. “Whether it’s a great ape or a New World monkey, it’s quite fascinating that the differences have been found or maintained in so many different species.”

Blood groups are unlikely to have lasted this long by chance. You have to give us an evolutionary advantage, said Segurel.

The ABO blood group gene not only affects our blood. It is also active in a wider variety of tissues and organs, including our digestive or respiratory systems, Segurel explained. This can be important when our body is faced with infections with different blood types that offer protection against various pathogens and diseases.

According to the study results,

“The evolutionary interest in maintaining these (blood) types may not be related to their function in the blood, but probably their function in the respiratory or digestive tissue,” she said. “These are the two places where you have the most contact with viruses and bacteria – the places where you breathe in air and digestive tissue.”

“If you imagine a cocktail of pathogens … there could be a cycle where sometimes B is beneficial, sometimes it is A. If you go through these different preferences, you will get a population with different blood types.”

Although we don’t know exactly how, Segurel said that variation in blood type levels affects our susceptibility to various diseases. What we do know is that certain blood types are more susceptible to certain diseases.

For example, blood group B has been associated with a reduced risk of cancer; While group O has been associated with a lower risk of death from severe malaria, it appeared to be more susceptible to norovirus infections, the winter vomit beetle, which also causes diarrhea.

So what about corona virus?

A handful of studies have shown a link between the blood type and the novel coronavirus, although most affected a small number of people and some were not evaluated by experts.

A team of European researchers who published their results in the New England Journal of Medicine in June found that people with type A blood were 45% more likely to be infected than people with other blood types, and people with type O blood were only 65%. infected as likely as people with other blood types. They examined more than 1,900 seriously ill coronavirus patients in Spain and Italy and compared them to 2,300 non-sick people.

A similar effect was observed for healthcare workers in Hong Kong with blood group O during the SARS outbreak, in which 8,098 people were infected from November 2002 to July 2003 and which comes from the same family of viruses.
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There are two hypotheses about the connection between blood types and Covid-19, said Jacques Le Pendu, research director at Inserm, a French medical research organization. One is that people with type O are less prone to clotting problems and clotting has been a major cause of the severity of Covid-19.

He said it could also be explained by the likelihood that the virus would carry the infected person’s blood group antigen. Therefore, the antibodies produced by a person with blood group O can neutralize the virus if they are caught by a person with blood group A – similar to the rules for blood transfusions.

“However, this protective mechanism would not work in all situations. For example, a person of blood group O could infect another person of blood group O,” he said, adding that a protective effect is probably not great and the amount of antibodies is very different from person to person.

Type A people should not be alerted, nor should Type O people relax, said Sakthivel Vaiyapuri, associate professor of cardiovascular and toxic pharmacology at the University of Reading In the United Kingdom.

Vaiyapuri, in collaboration with Thi Qar University in Iraq, is conducting a blood type role study based on data from more than 4,000 people in Iraq who had Covid-19 and 4,000 who did not get sick. He said that early results suggest that Type O could have a protective effect, but it is not definitive. And considering how many underlying variables there are, any protection or other effect is likely to be quite minor.

For example, the idea that type O blood is protective does not match the pattern of Covid-19 infection in the United States. Type O blood is more common in African Americans, but infection rates are disproportionately high in African Americans.

“Group O shouldn’t think they won’t get this disease. They shouldn’t be walking around anywhere and maintaining social distance, nor should Group A panic,” he said.

“There are so many underlying factors. We consider this a respiratory virus, but it’s really a whole collection of things that we don’t yet understand,” he said.

Research on blood types has sometimes fallen between different academic disciplines, but a better understanding of why we have different blood types and the relationship between blood group antibodies and disease risk will likely help us to develop vaccines and new drugs, including for Covid-19.

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