Some people develop more severe forms of the Covid-19 virus than others. On the other hand, people with the blood type O also the most common are less affected. This phenomenon could significantly slow down the spread of the coronavirus.
Different risk factors have been identified for Covid-19. The mortality rate increases sharply in the elderly, patients with chronic respiratory and cardiovascular diseases. Diabetes, hypertension, obesity and smoking also promote serious forms of the disease.
Blood type A: mortality rate 20% higher
Wang Xinghuan and his colleagues in the hospitals of Wuhan and Shenzhen examined 2,173 patients with CoV-2-SARS and calculated that people with blood type A had a mortality rate 20% higher than people with other blood types. Group O patients, on the other hand, had a 33% lower mortality rate. Even when age and gender are taken into account, these differences persisted. “Blood type A patients infected with CoV-2-SARS should be monitored with extra vigilance,” say the researchers.
The protective effect of anti-A antibodies
This discovery had already been made in previous SARS research in 2003. A study in 2005 showed that patients with blood type O were less likely to get the disease. This can be explained by the presence of anti-A antibodies (absent in group A and AB patients), which block the interaction between the surface protein of the virus and the conversion enzyme 2, which acts as a cell receptor. “Anti-A antibodies therefore provide natural protection against the virus”, explains a team of researchers from Inserm (France) in another study published in Glycobiology in 2008.
They also built a mathematical model that takes into account the different blood groups and found that ABO-polymorphism “can significantly reduce the spread of the virus, affecting both the number of infected and the kinetics of the epidemic. This is because the O and B blood groups (with anti-A antigens) make up the majority of the population (although the frequency varies greatly by region and ethnicity). In the US, for example, 44% come from group O, 42% from group A, 10% from group B and 4% from group AB.
Blood antibodies to slow coronavirus
However, the level of anti-A and anti-B tends to decrease over time in developed countries, “possibly as a result of improved hygiene”, the study suggests. Therefore, it may be worthwhile to increase anti-A or anti-B levels in all populations in order to slow down and limit the spread of some emerging pathogens. This may be an effective prevention strategy, not only for SARS but also for other coronaviruses, which cause a significant proportion of the common cold and may contribute to more serious respiratory tract infections. The study, which was published in 2008, is now proof of the bias.