Since the start of the Covid-19 pandemic, several risk factors for developing a severe form of Covid-19 have been identified. It is thus proven that age is an aggravating factor of the disease. The older the age, the higher the mortality rate. Patients with chronic respiratory and cardiovascular diseases are also at higher risk. Diabetes, hypertension and smoking also promote serious forms of the disease.
The role of the blood group
According to a new study carried out in China in three hospitals in Wuhan and in Shenzhen, people belonging to blood group A are also more sensitive to the coronavirus. The study was published in the journal medRxiv .
On average, in the Caucasian population, there are
42% of people in group O,
44% of group A,
10% of group B and
4% of the AB group,
according to the Red Cross .
Dr. Wang Xinghuan and his colleagues reviewed 2,173 cases of patients with Covid-19 . Among this group, they found that people belonging to blood group A had a 20% higher mortality rate . Conversely, people with blood type O, have a 33% lower mortality rate.
When researchers take age and gender into account, these differences remain, according to the study. They therefore insist on the fact that patients in group A must be subject to increased vigilance on the part of the nursing staff.
Another 2005 study on the SARS epidemic (2003) found that people in group O were less likely to contract the disease because they had antibodies than people in groups A and AB did not. .
Can we therefore draw general conclusions on the basis of these two studies?
According to the Science and Health website , the answer is mixed. The Chinese study is not sufficient to draw conclusions. “Based on this research, it cannot be said that a person with blood group A is more or less likely to be infected with the new coronavirus than a person with blood group O”, they write.
This is also the opinion of virologist Marc Van Ranst that we interviewed. He warns that the Chinese study has not been read and commented on by the scientific community.
It is indeed an observational study which cannot demonstrate a cause and effect relationship. In addition, the study does not detail the groups that were studied and there is no control group. “Which is a problem for the scientific validity of the study”, deplores Marc Van Ranst. It is also unclear whether the group is representative of the population.
In addition, the findings are based on figures from only two provinces in China and the results differ from region to region. In the Wuhan region, people with blood group A are more often infected. While in Shenzhen, it is actually the AB blood group that is most at risk. According to Marc Van Ranst, there is a need for further studies on the cases in Europe.
Coronavirus & blood group
Finally, the difference between blood groups A and O is not as great as it seems, says Marc Van Ranst. “This is an interesting study, but these results must be confirmed by other scientific studies which will probably show that the blood group does not play such a large role,” he said.
He also recalls that the other proven risk groups are proportionally much more at risk from the virus than people of blood group A.
The researchers use a very sensitive statistical method, which allows them to highlight small differences more clearly. In reality, the difference is rather small and irrelevant in practice. If it is therefore too early to alert the population on this point, the virologist nevertheless indicates to us that he will not fail in the future to take note of the blood group of the patients.
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