People with blood type A may be more vulnerable to infection by the new coronavirus, while those with type O seem more resistant, according to a preliminary study of patients in China who contracted the disease known as Covid-19. Medical researchers in China 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. They 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...