Of 206 patients who had died from COVID-19 in Wuhan, 85 had type A blood, which was 63 per cent more than the 52 with type O

According to a preliminary study of patients in China who contracted the coronavirus, people with blood type A might be more vulnerable to infection by the new virus while those with type O seemingly more resistant.

Chinese medical researchers took blood group patterns of more than 2,000 patients infected with the virus in Wuhan and Shenzhen and compared them to local healthy populations, reported the South China Morning Post.

The research found that blood type A patients showed a higher rate of infection and they tended to develop more severe symptoms. While the researchers said the study was preliminary and more work was needed, they urged governments and medical facilities to consider blood type differences when planning mitigation measures or treating patients with the virus, known as Sars-CoV-2.

"People of blood group A might need particularly strengthened personal protection to reduce the chance of infection," wrote the researchers led by Wang Xinghuan with the Centre for Evidence-Based and Translational Medicine at Zhongnan Hospital of Wuhan University.

"Sars-CoV-2-infected patients with blood group A might need to receive more vigilant surveillance and aggressive treatment," Wang added.

In contrast, "blood group O had a significantly lower risk for the infectious disease compared with non-O blood groups", according to a paper published by the researcher team on Medrxiv.org on March 11.

Of 206 patients who had died from COVID-19 in Wuhan, 85 had type A blood, which was 63 per cent more than the 52 with type O. The pattern existed across different age and gender groups.

"It might be helpful to introduce ABO blood typing in both patients and medical personnel as a routine part of the management of Sars-CoV-2 and other coronavirus infections, to help define the management options and assess risk exposure levels of people," the report stated.

Scientists and doctors from cities across China including Beijing, Wuhan, Shanghai and Shenzhen participated in the study. It has not been peer reviewed, and the authors cautioned that there could be risks involved in using the study to guide current clinical practice.

Gao Yingdai, a researcher with the State Key Laboratory of Experimental Haematology in Tianjin who was not involved in the study, said it could be improved with a larger sample size. Though 2,000 was not small, it is dwarfed by the total number of patients infected by the coronavirus, now exceeding 180,000 globally.

Admitting the limitations of the study, Gao said it did not provide a clear explanation about the phenomenon, such as the molecular interaction between the virus and different types of red blood cells.

She remarked that the new study "may be helpful to medical professionals, but ordinary citizens should not take the statistics too seriously".

"If you are type A, there is no need to panic. It does not mean you will be infected 100 per cent. If you are type O, it does not mean you are absolutely safe, either. You still need to wash your hands and follow the guidelines issued by authorities," she added.

Austrian biologist Karl Landsteiner discovered the main blood groups in 1901 and named them type A, B, AB and O. Blood types are determined by a so-called antigen, a material on the surface of red blood cells that can trigger an immune response. The discovery allowed for safe blood transfusions by matching blood types in patients.

Blood types vary in a population. In the United States, about 44 per cent of the population is type O, while about 41 per cent is type A. In Wuhan, which has a population of about 11 million, type O is 32 per cent, while A is 34 per cent among healthy people. Among COVID-19 patients, it was about 38 and 25 per cent.

According to previous studies, blood type difference has been observed in other infectious diseases including Norwalk virus, hepatitis B and severe acute respiratory syndrome (Sars).